I recently helped my dad to clean out his loft in preparation for its being re-insulated. We uncovered a real treasure trove of fond memories.
I was particularly delighted to find lots of old books from my childhood, which I had thought lost—including some old school exercise books from both my primary and secondary schools. There were also numerous nature-related children's books, including my precious I-Spy books, The Observer's Book of Birds (my first ever bird book), some animal encyclopaedias, and a couple of young naturalist's handbooks.
My copy of Leonard Moore's The Young Naturalist's Handbook has already proved useful in identifying a greater stitchwort found in the local woods, and a lumpsucker a friend found washed up on his local beach. The book uses the elegantly simple technique of sorting species according to the habitat you are likely to see them in, making it relatively simple to flick through and find what you're looking for. Contrast this with the half-hour I spent unsuccessfully trying to identify the greater stitchwort in a grown-ups' flower book.
It seems to me, in this hyperlinked, cross-referenced, search-engined age, that it should be a lot easier for amateur naturalists young and old to identify mystery species. Fortunately for me, however, I now once again have my trusty Young Naturalist's Handbook to hand.