A new fully revised and updated edition of Beatles Undercover (1998) and Beatles Deeper Undercover (2010). This enlarged edition brings the Beatles' musical story up to date with entries all the way into 2022. Substantially revised, Kristofer Engelhardt has once more brought this essential work up to date for Beatles' fans everywhere. Here are some quotes about previous editions.

Goldmine Magazine: This outstanding book is simply the most exhaustive body of work to date to document the known contributions made by The Beatles (as a group and individually) to the recordings of other musical artists. Beatles Undercover is a tremendously valuable contribution to The Beatles' literary canon, and deserves to be added to the library shelf of every serious fan of the group. Rock music fans in general will discover a wealth of musical and historical gems contained within these pages.

Record Collector Magazine (UK): Engelhardt's discographical detail is remarkable, making this a must-buy book for any serious Beatles collector. One of the five best rock books of 1998.

Roy Cicala (John Lennon's recording engineer): This book stands alone as the last word on The Beatles' work for other artists. The research and attention to detail are astounding.

Formby Times (Liverpool, UK): This is a monumental, scholarly work and will appeal to those who want to follow the development of The Beatles as individual artists. It is highly professional and will, in my view, become recognized as the standard work in this field.

Q Magazine (UK): Tirelessly catalogued, exhaustingly comprehensive, three stars.

Beatlefan Magazine: Only a few titles can be considered truly indispensable for collectors of Beatles' music. Beatles Deeper Undercover is one of those indispensable titles.

Beatlology Magazine: Painstakingly researched, thoroughly documented, and entertaining to read, Engelhardt's Beatles Undercover is a reference book that any Beatles completist will want to have.

Discoveries Magazine: It's usually possible to find one or two inaccurate statements in a Beatles book, but I didn't notice any in Beatles Undercover. Engelhardt gets it right. Such diligence is typical of this book, which seems to be the definitive look at the Fabs' extracurricular work.

Houston Chronicle: Beatles' fans, rock addicts and trivia crazies will pore through Beatles Deeper Undercover, dog-earing pages and underlining "I didn't know that" stories in each section. I loved this book (Ken Hoffman).

Jeff Lynne: Kristofer, Well done, the book is amazing!

George Harrison: K. What a book! A massive job.