Great book for modelers, there is a lot of detailed, crisp color photos. Lots of line drawings a just a bit of the history of a very successful artillery vehicle that is still in service since the 1960's.
Published in 1990, it does not have photos of the newest M109A6 Paladin, which is a huge upgrade to the M109 design.
Verlinden "Warmachines" series is aimed for the Modelers market. A nice book to round out a collection. The New Vanguard book has more history and is more recent. Both are about same price.