I have over 50 decks, some I use, some are just part of my collection.
Some I buy with real companion books, some do not have that option, but do include a many page booklet, that has staples (staples are the key indication of a real, maybe small, but real book) that fits in the box with the deck. These are just as good as any companion book as long as your eye sight is good.
Now the little fold'em leaflette type 'book' are nearly useless. Card meanings are dry and limited.
I tend to read the leaflettes over once and then toss them into a box, saving them in case I choose to send the deck off into anothers hands.