I agree with Betty, based upon a quick review of the Amazon web page for the book.
http://www.amazon.com/Avenging-Lincolns-...%27s+death
The product detail shows 246 pages. If you click on the image of the book, "look inside", the table of contents shows there are fewer than 170 pages of text, slightly less than 70% of the books total printed pages. The book does have an extensive index of over 35 pages, that seems a lot for only 170 pages.
Based upon the table of contents this book appears to take a legal view of the case and trial of the conspirators, with the last chapter entitled An Unconstitutional, Unfair Trial.