The book is a condensed source of information of various different subjects relating to organic chemistry. In saying so it is a general overview of practical organic chemistry. Sykes is clear in his explanation and elucidation on various reaction mechanisms and as he states early on, he does promote a mechanistic perspective of organic chemistry.
Sykes is particularly useful for individuals who have done introductory organic chemistry and are venturing into deeper topics of the subject, i.e. stereochemistry and synthesis as examples (a lot of universities offer courses which purely concentrate on these regions of study).
Now the greatest downfall I see about the text is the price. March's advanced organic chemistry is much more extensive, newer and my personal opinion is that the authorship is better in March's
Another downfall is the age, although a lot of the topics that have been introduced in this book have not changed significantly and therefore dont seriously affect the text's validity; I still feel it should have had an update. This book was published in the 1980's (the late era of the decade).
All I am saying is that Syke's book is a classic, one can learn a lot from it and it is a fairly good reference book, however to my understanding there are better texts of the same genre covering practically the same themes as in this book.
I would strongly recommend any individual interested in this book to have a look at March's Advanced Organic Chemistry.