ook这个词应该是相当的可数（countable）.
它在作“图书”（a set of printed pages that are held together in a cover so that you can read them）、“笔记本”（a set of sheets of paper held together in a cover so that you can write on them）、“册/集”（a set of things such as stamps,matches,or tickets,held together inside a paper cover）的时候,是绝对的可数.
有时候,必须要用复数,也是可数的表现,比如：当表示“account”的时候（written records of the financial accounts of a business）,多用复数,e.g.An accountant will examine the company's books.
还有一些固定搭配,也可以体现book是可数的：
by the book：exactly according to rules or instructions
a closed book：a subject that you do not understand or know anything about
但也有一些情况,他并没有配冠词,而是单独使用,非常少见,例如：
in my book：【spoken】said when giving your opinion:
e.g.In my book,nothing is more important than football.
bring somebody to book:to punish someone for breaking laws or rules,especially when you have been trying to punish them for a long time:
e.g.War criminals must be brought to book.
所以,总的说来,book是比较确定的可数名词.