Books have nothing in common with gambling except for the books about gambling.
If you enjoy the book, your payout is those feeling of enjoyment. If you lose, the price is the cost of the book and the time you wasted reading it - but you have the paltry consolation prize of a now-second-hand book that you can sell at a loss to a used book shop.
And you can affect your odds of winning or losing, by going with a genre or author that you already have an affinity to (or not!)
I could be said to be gambling that my comment will be read. I am also gambling that someone will not disagree with me. I am gambling that by writing this comment I'm not wasting time that could have been better spent in other endeavors. I am gambling that I will not die of a stroke just after writing my comment, making my final conscious act a pointless one.
If it sounds absurd, that's because it is. Of course it's not gambling, and neither is reading a book.
I think cryptokitties is somewhere between Poker and Slot machines.
When I buy a book, I usually don't know its contents beforehand (the exceptions are I had copied it somehow in my earlier years, and now I want to buy it to come clean, or it is a classic I just never bought yet).
Most of the time, I rely on a friends reference, or a review online, or maybe I just buy by chance. And in either of these cases, there is a less than 50% chance I perceive the book as good. Which, to me, is a gamble. So I suppose there is an edge I don't get?
Gambling is I give you $X I have a,b,c % chance of getting A,B,C. Usually I get nothing. Nothing I can do can effect the outcome.
Colloquially, you might say "I don't like this author, but the reviews say blah was a blah, so I took a gamble". But that is clearly not the same as pure chance gambling.