The structure of the Book Review could be in any form. Keith wrote his review in the form of a letter, which has been very successful. Hence, you could write it in letter form or in a standard review essay form. Word limit varies depending on the text being reviewed.
Although I do have a few titles listed, you can review something you have already read and reviewed for your thesis. Or,again, if there is a text that I have not listed, that you wish to have and review, just say the word.
Good luck with the thesis (is this the viva?)! Will look out for a message from you then ;-)
If you are bored and want something to do, you can always write a review for me. This could be a book that you would like to get your hands on, or a book you have already read. Definitely, something to have fun with, as the more creative the better. Keith has submitted one in the form of a witty letter. Really interesting Stuff! (ironically, the book Keith is reviewing is Danny Miller's Stuff). Let me know if you are interested.