When I was last home, I found my first field guide (in the attic) given to me by my parents at Christmas 1983. The Easy Way to Bird Recognition by John Kilbracken featured only 184 of the most common species of the British Isles, but was fine for a young beginner. The cool thing about it was the idea behind it was unique in the bird book market at that time. A simple systematic key was used, guiding you through a sequence of questions designed to eliminate unlikely candidates while narrowing the field in the search to identify your mystery bird. Juvenile and immature plumages were not featured, making it somewhat limited but I do remember it was a lot of fun.