Species Epilachna borealis - Squash Lady Beetle
Coleoptera or Beetles east of the Great PlainsBy Edwards, J. Gordon
Edwards Brothers, Ann Arbor, MI. 181 pp., 1949
Obviously the taxonomy is a bit dated, but the text has great discussions of many genera and subfamilies. I estimate roughly 500 detailed line drawings of antennae, tarsi, ventral details, etc.
"It contains an original, simplified, and completely-illustrated key for the identification of beetle families east of the Great Plains, a discussion of the appearance and habits of the various adult and larval forms, and a useful up-to-date  bibliography for each family."
Lithoprinted from copy supplied by author.
Gordon, E.J. 1949. Coleoptera or Beetles east of the Great Plains. Edwards Brothers, Inc., Ann Arbor, MI.
The Beetles of the Pacific NorthwestBy Hatch, M.
University of Washington publications in biology, Volume 16. University of Washington Press, Seattle, Washington, 1953
[1953-1971] Covers the Beetles known to occur in British Columbia, Washington, Idaho, and Oregon. Part I provides an introduction and covers the Suborder Adephaga. Part II covers the Suborder Staphyliniformia. Part III covers the Family Pselaphidae of the Staphyliniformia, and part of the Suborder Diversicornia. Part IV covers the Palpicornes and Heteromera. Part V covers the Phytophaga, Rhynchophora, and Lamellicornes
The Beetle Fauna of Rhode Island, an Annotated ChecklistBy Derek Sikes
Rhode Island Natural History Survey, 2004
Volume 3 of the Biota of Rhode Island. An important reference covering over 2000 species of beetles known to occur in our area. Fifteen page introduction, followed by checklist with scientific and common name, synonyms, abundance, and collection notes and host information for most species. Softbound, 328 pages.
Introduction to North American BeetlesBy Charles S. Papp
Entomography Pubns, 1984
Out of print, but worth finding if one is interested in beetles. (Bioquip had a few still in stock in 2003.) Almost 1,000 (black-and-white) illustrations, and some life history information. Papp's scratchboard llustrations are excellent, even artistic.
Note: I do not know how many of the illustrations and species accounts of this work are included in Papp's A Comprehensive Guide to North American Insects--there could be considerable overlap. I have not seen the latter work.
A Manual of Common Beetles of Eastern North AmericaBy Dillon, Elizabeth S., and Dillon, Lawrence
Row, Peterson, and Company, 1961
This is long out-of-print, but can be found on the used market. Though old, it is still an extremely useful reference. Has approximately 1,000 good black-and-white illustrations and several pages of color plates. Coverage of widespread, strongly-marked species is quite good. Has keys as well, which can be used by the amateur with a little luck. This is my first choice for identifying an unknown beetle. Taxonomy is out of date in many cases, so names must be used with care.
Original (1961) hardback edition was in one volume. There was a Dover reprint, circa 1971, in two volumes. (Be sure to get both volumes if you are buying that reprint edition.)