At approximately 9" x 11" in size and 511 pages in length, Robert J. Nixon's Their Silent Vigil: A Complete Guide to the Monuments of the Gettysburg National Military Park, Volume One (Tate Publishing, 2009) is a large book that puts its hefty dimensions to good use. It (in conjunction with a future volume) attempts an inventory of all Civil War monuments placed at the Gettysburg National Military Park. The author differentiates between monuments, markers, and tablets, relegating the latter two categories to a number of tables located in the forefront of the book.
At its heart, the volume is a collection of detailed line drawings of each Union monument (think detailed engineering drawings, with front, back, and side views). These are arranged by state and service branch. A handful of Confederate monuments are present, with the rest presumably reserved for the second volume. There is no narrative beyond the introduction and brief explanatory notes.
The complete text inscribed on the monuments is reproduced, as well as any applicable stone, marble, or bronze artwork -- i.e. sculpture, bas relief, etc. features (either in drawing or photographic format). Shading provides depth to the drawings, as well as information about materials used and roughness/smoothness of the cut. Monument dimensions (L x W x H) are labeled and photographs of each monument are also included. My only real problem with the presentation is the vagueness of the physical location given for each monument site. Only the street name is indicated, when perhaps a numbered map or GPS coordinates would have been in order. A full index would have been helpful to the reader, as well, but perhaps the second volume will accommodate one.
The above minor reservations aside, I think most Gettysburg enthusiasts will find Their Silent Vigil to be a useful and attractive reference book. I've come across nothing quite like it on the market.