I love book tests. They are one of my favorite things to perform. I never found a "out of the book" book test, I had to combine elements from a bunch of different ones to find one that suit me. I don't know if your luck will be the same but its something to think about.
I have the three digit to 1089 one, then I have one where you use a quarter or coin of some kind to force a page. Then you just force the first word that they see.
As far as what am I looking for, honestly, I don't know. I just want to roam some other ones, and see what I like. I don't like math questions, because those can be figured out too easily (even before I was a magician I was figuring these ones out). Mainly I just want to see what else is out there, and maybe I would like that instead.
As mentioned before, the Mother of All Book Tests (MOABT) by Ted Karmilovitch.
For a walkaround booktest: Try Luna from Outlaw Effects.
For an impromptu booktest: Try Alain Nu's Work Works II (But get Work Works I as well, although that's not impromptu, but still brilliant).
For a recent booktest: Try Devin Knight's Wordsight.
For an out of book booktest as requested above (I assume you mean, a booktest that doesn't stick with a book: Try The Billion Monkeys Book Test by Joshua Quinn in ParaLies.
And my personal favourite for booktests: Jon Thompson's Naked Book Test. Absolutely brilliant. I've done this over the phone and the internet as well. Any book, any page, any word, completely impromptu.
Please note that these are just some suggestions to look up for each category. I do not have most of these, I cannot vouch for most of these - but I've heard good things about all of them, and they're worth checking out.
I use a Tossed Out Book test that uses Hoy's principle.
I also use a book test that you peek a certain word on the page facing you and it matches up with the word they are looking at on the opposite page but there is no way for them to know that. Not sure what the exact Book Test name is but is is very easy and ingenious. Bought it at a magic auction for 8 bucks.