I don't know that I'd call this an "uncommon" field guide, exactly, but it's certainly a very good one, if rather exhaustively detailed in some places. It's also an American field guide, and while there's a lot of crossover from introduced trees - you can find an oak or a chestnut in most places - it will of course be of more use in that country.
It's a good book for beginners, too, I think. Full of resources, and if each entry begins with the standard information that you'd find in any field guide, the bulk of every entry comes after that, in a short essay on history and context of the tree in question. These are genuinely accessible pieces of writing, geared to the interested non-scientist. I do wish there was a bit more variety in them, however. More information on mythology and ethnobotany, and less information on which random US President planted what when they were at the White House, for instance. I wonder if, in a book like this, that extra material might have been gathered from various nature writers, in more of an anthology/supplemented field guide type of book. This would have the benefit of a bit of diversity in the writing, which might have made it feel a little less repetitive. Because valuable as this is, it took me months to wade through...