In the absence of a clear context regarding how known or unknown is the number of books available for me to read, should I use what book to read or which book to read?
I don't know what book to read (= I don't know how many books there are for me to choose from.)
I don't know which book to read (= I know how many books there are for me to choose from, and choose one from that specified number.)
Are these assumptions correct or not? If not, why?