Seattle typewriter collector Nick Bodemer has put out a new, 52-page book on typewriters called Mid-Century Portable Typewriters - A Spotter's Guide.
It's "a guide to the most commonly-found typewriters. These include typewriters made between 1936 and 1970, with a focus on compact portable typewriters".
I haven't seen a copy of the book, but Nick did send me a few pages, which can be read below, to give you an idea of the contents.
The Amazon "About the Author" blurb says, "Nick Bodemer has been collecting and researching typewriters for 10 years. His first typewriter was a light blue Royal Safari, made circa 1967. He researches and photographs typewriters, and writes the blog royaltypewriters.blogspot.com. He lives and types in Seattle." A biography line reads, "I am an avid typewriter collector and researcher who wants to help others identify commonly found portable typewriters, and learn more about them."