While most books will give you general information about the converted LCM-6s used on South Vietnam's rivers, this book has great coverage about each type of boat, whether troop carriers, monitors, support boats or their variants. Each of these is covered in minute details, describing the conversion process, armament, armour and operational use and markings.
The only thing missing is a set of scale plans but that is more than made up for by the large number of clearly captioned photographs (127 colour and 96 black and white photos photos, most of them hitherto unpublished), including a whole lot in full colour and by top- and side-view drawings detailing the typical colours and markings worn by the amphibious craft. Note that scale plans for the ATCs and ASPBs are available in Norman Friedman's U.S. Small Combatants, Including PT Boats, Subchasers, and the Brown-Water Navy: An Illustrated Design History (US Naval Institute, 1987) if you are lucky enough to own a copy of this long out-of-print book.