I've seen a lot of threads recently where people confess (one way or the other) to poor tree species ID skills. As I'm sure we'd all agree, your species ID skills are crucial as so many functions, properties etc are dependent on species (as well as season, part of tree, form....)
A quick search on ebay at the moment (search under "forestry") will uncover 2 books - know your conifers and know your broadleaves. These are nice books which are out of print but well worth getting hold of. I've had my set for a while. In particular, the broadleaves book is quite rare in that it pays attention to the form of the buds - a key ID feature often overlooked.
good luck on that one
Disclaimer - No connection to seller at all, just trying to be helpful
A quick search on ebay at the moment (search under "forestry") will uncover 2 books - know your conifers and know your broadleaves. These are nice books which are out of print but well worth getting hold of. I've had my set for a while. In particular, the broadleaves book is quite rare in that it pays attention to the form of the buds - a key ID feature often overlooked.
good luck on that one
Disclaimer - No connection to seller at all, just trying to be helpful