Mark Roehrig, ISBN 1-55369-653-0

The very first "How-to-book" enabling you to experience the thrill of owning and operating your very own amphibious car, more affordable than ever. It will show you the simplest way to build the works that will turn your land locked car into a capable, reliable amphibian. It is NOT specialized on the Geo - it can be used to convert ANY road vehicle into amphibian. Many drawings and b/w pictures. 
If you have always dreamed of building your own James Bond car, this is the point to start with. Can´t miss it.

133 pages. Price: 22,95 US$ (shipping included inside US).

Also available as VHS video tape for 17 US$ or both for 39,95US$ (included shipping inside US).
Shipping outside USA and Canada add 6,-US$ for the book only or 8,-US$ for both.

Wings & Wheels Publication, ISBN 80-86416-12-7

It is meant as a photo manual for modelers. Indeed the 50 coloured pages are filled up with plenty of detail photos of the VW Schwimmwagen type 166. Could be useful for everyone restoring a type 166 back to original. Or for everybody who simply loves high quality pictures of this German amphibian jeep.

Price: about 20,-US$

Available at www.discountmodels.com

Ben Carlin, Tynron Press, ISBN 1-871948-91-6

The complete amazing story of Ben Carlins world circumnavigation in an amphibious Jeep! He even crossed the Atlantic Ocean. 
This book is including the first part of the journey described in "Half-Safe, across the Atlantic by Jeep" (see antiquariat) and follows up with the completition. Most incredible to read, just sometimes Carlin´s got a bad Australian accent.

Price: 9.99 GBP  (approx.16,-US$)

Available at amazon.co.uk(not in stock)
or you can purchase it directly from Guildford Grammar School Archivist Rosemary Waller for 27,50$ + shipping

Boye DeMente, Phoenix books, ISBN 0-914778-01-3

Boye DeMente joined Ben Carlin on the part across the Pacific Ocean from Japan to Alaska. He was an US journalist and had to wait 5 years until he was allowed to publish the story of his life time adventure. That was the deal with Carlin. In DeMentes book you will learn the amazing Half-Safe story from a different point of view and lots of new information. This is the 2nd edition.

Price: 20$ + shipping

Available at Ian Grieve

compiled by Trevor Alder, Transport Source Books Ltd, ISBN 1-85847-300-4

Roadtests, articles and adverts mainly on Amphicar, but also on Amphi-Ranger, Argo, Meyer and Trippel. Includes a couple of nice Amphicar jokes.
Printing is a bit poor like from a photocopy machine. But still a must for Amphicar fans.

Price: approx. 15,- US$

Available at Transport Source Books Ltd

R.Sawicki, Books International, ISBN 83-906942-1-2

About the Volkswagen Kübel- and Schwimmwage during wartime. Can´t say much more than there are many b/w pictures inside, because I can´t read Polish.
Paperback, 70 pages, Polish only! 
Available at:

Books International
101 Lynchford Road
Farnborough, Hampshire GU14 6ET
England

René Pohl, Heel-Verlag, Königswinter ISBN 3893657029

Hasso Erb, Motorbuch Verlag Stuttgart, ISBN 3-613-01165-4

Hardcover 1988, describes the wellknown amphibs like Amphicar, Ford GPA, VW Schwimmwagen, and most Trippel prototypes and some other cars. Half of the book contains the amphibious trucks like the DUKW, Toyota Suki, EWK Bison, Alvis Stalwart and several others.
Used to be the standard cataloge of amphibious cars & trucks before the book "Mit dem Auto baden gehen" came out. Still it is the second best book in that subject you could get. Unfortunately for you, it is also only in German and out of print.
But it can be found quite easy in German antiquarian bookshops. I am not sure, but I heard it is also available from Hugh Gordon Imports.

Hans-Georg Mayer-Stein, Karl Müller Verlag, ISBN 3-86070-861-9

Some more wartime pictures of Beetle, Kübel- and Schwimmwagen. Describes the Volkswagen history during the Third Reich and its vehicles.
Hardcover, German only! Out of print!

Helen & Frank Schreider, Secher & Warburg Ltd. 1957

Helen and Frank Schreider and dog Dinah tried the Panamerican Highway even before it was built. They did the trip from the northest town of Alaska to the southest point of South America in a converted Ford GPA. Very interesting story. Hardcover copy includes couple of photos and illustrations.
Very hard to find! Better seek out for the copy below:

Helen & Frank Schreider, Frederick Muller Ltd. 1963

This time the Schreiders and their dog Dinah were exploring  the Indonesian islands. That for they converted a second amphibious GPA into La Tortuga II. With that they did a lot of island hopping. The story itself is same impressive as all those adventure stories, but from the amphibious point of view it is a bit disappointing, as La Tortuga II is very much in the background and one picture only displays the unconvential vehicle.

Instead I recommend to seek out for the following back issues of National Geographic magazines:
October 1960, May 1961 and August 1962. Those contain the Schreiders journey through India and also through Indonesia to Timor. Of course the story is cut compared to this book, but in difference to the book many coloured pictures of La Tortuga II can be found in the articles.

Virginia Hamilton, McGrawhil book company,1962

Really funny and oddy story of Virginia Hamilton, her husband, her four daughters, three college boys and a dog, travelling from New York to Buenos Aires in an amphibious DUKW.
Hardcover, includes photographs and illustrations. Great story!

Jeff Woods, ISO Publications, 1978

Maybe the pre-brochure of "Duck in action"(see above). Many pictures, very detailed and lots of information about the DUKW. Even all dashboard plates are displayed.
Paperback, 72 pages!