The book contains several different approaches to the Feynman integral and discusses in some detail relationships between these approaches. The exposition is very clear and detailed and the proofs of results in the text are detailed and extremely well written. Also, the text contains many items that have only appeared in the research literature. Some of these results are quite new.
Also contained in this text is a thorough discussion of Feynman's operational calculus, again from more than one point of view. Many of the results contained here have only appeared previously in the research literature and again some are quite recent. This part of the book is also very well and clearly written.
There are also many remarks and examples dealing with the applicability of the formalism to physical situations.
This is a great read for anyone wanting to further there knowledge about these subjects.