Simply from a perspective of time investment, I find most of Unknown Mentalist stacks are very easy to learn and from an academic perspective, most of them are based on a brilliant and novel basic idea. First I was impressed from a learning angle for his first 1 or 2 stacks and then I became a stack collector - trying to see what more could he create or discover in a rather crowded 'stack field'. As we know there are 52! unique stacks that can possibly exist.

But my overall stack knowledge is very limited to the study of these stacks other than UM stacks - Stebbins, Eight kings, Bart Harding, Nikola, Mnemonica, Gauci, Solka, Dani Daortiz, Aronson.

I'll try to keep the reviews brief but informative. These could be colored by my own bias as is normal for an admirer.

1. Karma Deck and all its variants - Personally I like this the most and use it the most. And I have already reviewed it on a different thread in detail.

2. Sloka Deck - This is a tetradistic stack. Useful as a sequential stack and can also easily be used as a memdeck with just a bit of extra effort. I literally learnt the stack in under a minute. Learning the random suits took me another couple minutes with the dead simple method. It is described as 'worlds smallest mnemonic' for a stack and I think that is very true. The 5 variations of the main stack are also equally easy (2 of these maybe a bit less easy than others). So I can learn 6 stacks totally based on the same basic idea. An interesting 'reverse' process of readings and a couple routines are given.

3. Optik Deck - This is a monodistic stack. Basically a memdeck based on a brilliant idea. The card value and card position are linked to each other with a crazy easy visual hook. It is difficult to explain without giving away the secret. Lemme say if I just look at the card value and card position, I can remember the association for life. It is that easy (for a majority of the cards) There is neither mnemonics nor math nor algorithms nor brute memorization. I got this down full and complete in about 15 minutes. Here too several variations are possible as given but I have not tried them out yet.

4. Monk Stack - This is a tetradistic cyclical stack based on yet another novel idea. I just read a single page and understood the entire stack. I guess one can learn this stack in about 5 minutes. The novel idea is based on our 'existing' knowledge of card values and so there is nothing new to learn. Just knowing the principle will give you the stack. The manuscript does not give any suit randomization method but I guess now I know several ways to do that (for any stack rather). An alternative stack based on the same principle is also mentioned.

5. Spell Deck - This is a tetradistic memdeck. Basically, it is a superb evolution of the basic idea or principle behind Monk Stack. And equally easy to learn. I could learn this in just about an hour - including random suits and all. 3 other variation stacks are also included. This ebook also includes another ebook - Suit Order Systems Volume 3 - which gives several easy methods to randomize suits of practically any stack. There is also yet another ebook included here. The Prime Deck ebook.

6. Prime Deck - The Prime Deck which is yet another tetradistic memdeck based on a totally different principle and several variations is part of the Spell Deck ebook. Overall this was great value for money and great learning for me.

7. Know Stack - Well I think Know Stack is simply a genius idea. Although a tetradistic cyclical stack, with just a bit of effort can be used as an excellent memdeck too. I could learn this just about 30 minutes. The basic idea takes less than a minute to 'know'. The simple suit randomizing idea which is explained is equally genius, imo. A couple of alternative stacks based on the same idea are explained. This ebook also includes the Dates Deck and Cue Stack. Fantastic value for money for the quality material included.

8. Dates Deck - It beats me why no one could think up such a simple idea to make a stack. Just from some dates which I already know, this stack simply jumps out at you. This is a cyclical tetradistic stack. A couple variations are also explained. One can even completely personalize this stack. This is part of Know Stack manuscript.

9. Cue Stack - A very interesting idea indeed. Based on a single 'cue' statement, one generates an entire stack. Totally 3 Cue Stacks are explained. This is a sequential tetradistic stack. This is also part of the Know Stack ebook.

10. Lucky Deck - A simple algorithmic stack based on a killer principle, I think. This is a tetradistic memdeck with randomized suits. Just 3 simple rules and I got the entire deck in under an hour. And the best part is Lucky Deck can also be used as a cyclical stack which is also explained clearly. The simple algorithm or rule never allows you to forget the stack. This ebook also includes another ebook - Suit Order Systems Volume 5 - which gives several easy methods to randomize suits of practically any stack.

11. King Stack - This is an algorithmic tetradistic stack which can be used both as a memdeck as well as a cyclical stack. The rules for both are very easy. The suit randomization method is great. I was able to learn this in about an hour. An interesting which hand routine based on the stack is explained.

12. Her Majesty Deck - This is a tetradistic memdeck. The seed of the underlying principle here is hidden in letters and numbers and their unique combination, which is 'oh so easy' to grasp and learn. Once again the suit randomizing method is superb here. This ebook includes the Dictum Deck as a bonus. The Unknown Mentalist sure knows how to pack value into his ebooks.

13. Dictum Deck - It is a tetradistic sequential stack which is based on the same basic principle as Her Majesty Deck, which is why it is a part of the Her Majesty Deck ebook, I guess.This deck is based on a 'story sentence' much like the 8 kings stack but with a killer twist which I never saw coming. The suit system is random and very easy. And 3 alternative Dictum Decks are also explained - it was difficult picking which of these 3 stacks was the best. Once again this combo of Her Majesty Deck and Dictum Deck is a great value for money and great quality material.

14. Kalendeck - As the name suggests, this stack is based on the calendar. I am dazed how the Unknown Mentalist is able to pluck out a tetradistic memdeck out of a regular calendar which we all have been seeing and using all our lives. Absolutely brilliant, imho. Kalendeck has a random suit order. Again this ebook is packed to the brim with bonus material - Kronos Deck, Era Deck, CMC Stack, Almanac Stack - all are included.

15. Kronos Deck - This is a sweet variation of the Kalendeck. It was difficult for me to decide which was better among Kalendeck and Kronos Deck.

16. Era Deck - Although another variation of the Kalendeck, some of the basic ideas are very interesting and worth knowing.

17. CMC Stack - It stands for Cyclical Month Card Stack. It is also a tetradistic stack. This is based on some interesting ideas. But personally, I would not be using this - not because it is not a good stack, but because a particular feature does not suit my performance style.

18. Almanac Stack - Although based on the calendar, the basic principle is completely different from Kalendeck and extremely novel. The very process of learning this stack was a pleasure for me. Apart from the primary stack there are 4 more variations of Almanac Stack which are included. So overall a big bunch of stacks in this Kalendeck ebook. Great material and absolutely great value for money.

19. Fun stacks - Contrary to the name, these are pretty seriously usable stacks based on some killer ideas and principles. There are 4 different stacks explained along with some variations. The names of the stacks sure are funny, but the principles are simply brilliant. The 1260 Stack, the 78 Stack, the 8000 Stack and the 700 Stack - all have nothing to do with numbers or math but are created with some really smart thinking.

I do not yet have his Rasik Deck and Yogik Deck. Will review them whenever I am able to get them. Of course, I do not use all these stacks - just the Karma Deck and one other variation. But knowing the underlying ideas by itself was quite enriching for me.

But I do have and like his work on other stacks like Si Stebbins and 14/15 decks which I plan to review in a separate thread shortly.

And to quote the author in one of his ebooks, he is yet to release a majority of his stacks. Now that is astounding, given that he has released several stacks already.

Given that UM has created so many stacks out of so many cool ideas, I strongly suspect he must be seeing stacks everywhere - pretty much like Neo sees codes everywhere in Matrix.

I am yet to come across anyone in the long history of magic who has created so many quality stacks. An amazing feat by itself.