I would appreciate any book test specific suggestions anyone may have.
Keep the mentalism separate from the magic. There is nothing that weakens a demonstration of psychic ability than to follow it with "now I want you to pick a card...." There are good ways to transition from magic to mentalism in a show. Once you transition, you shouldn't go back.
Decide how you want to play the effect. Are you reading their mind, getting clues from their body language, using the fact you memorized the book or influencing them to pick a certain word on a certain page? Then script and act accordingly. Read the book and incorporate what you like about the book in your presentation to answer the question why you are using that book.
Don't emphasize the process. Too many people overstate how free the selection is. Let the spectator observe the fairness of the process themselves - don't recap, don't ask them if it is fair, don't explain they could have chosen any page or word, don't ask them if they want a different page. Play it as if they can pick any page they want to and it wouldn't matter. Similarly, don't mention or reference methods. Don't say "I'll turn my back so I can't see" - because that makes the audience think that there still is some way you can see. Don't say, "Don't show me the page" or anything else that hints at how you could do this. Rather, set up the script and blocking (how you move on stage) to dispel any methods. Show, don't tell.
For example, you could use something like, "In a moment, I'm going to ask to you pick
any page in the book and select a
random word on that page. Once you select that word, I want you to
just think of it. Don't say it out loud.
I don't want anyone but you to know the word." That pre-explains the selection process and puts the ideas in bold into the audience's collective memory.
Lastly, ACT. Go back to how you want the effect to play. If your presentation is that you have memorized the book, talk about what is happening in the book around where they selected their page. "You picked a page in the middle of the book. That is where [insert explanation]. I really like that because [insert something relevant to what is happening in the book. Do me a favor, read out loud a sentence from the middle of the next page." [After they read it]." Then go into the reveal.
If you are reading their body language have them visualize the word, not the letters but the meaning. Ask them "Does the word mean something like [insert synonym]. [They say yes]. I can think of a bunch of words that mean that." The have them think of the first letter as you say the alphabet. Name three letters that are around it. Then select the correct one after saying those letters again. Then OK, so you are thinking of a word that means [insert synonym] and begins with [insert letter]. Think for a minute and then reveal the word in a different tense, as a verb instead of a noun, as a plural rather than singular. Remember, an exact match is magic, getting the word right without being exact is mentalism.