Which Darwin book (and today edition) is illustrated by his own drawings?
I believe that there is only one drawing in the first edition of On the Origin of Species, and it is Darwin's.  Any good edition such as the fascimile edition with an introduction by Ernst Mayr, will include this drawing.  I'm not sure about other editions of the Origin or other books of Darwin's.  However, maybe you don't need to buy anything.  Darwin Online is a wonderful collection that includes many (all?) of Darwin's writings over the years, including images of many of them; the drawings are no doubt included.  

It's possible that the History of Science and Mathematics StackExchange site would be a better place for this question.