A judicious review by Paul Weimer of a great NESFA volume linked below.
I liked this book a lot, but for me the most distinctive feature of this series is the one that I like least: the stories are a mixture of early & late. I’d prefer a chronological ordering, or an ordering by series, or some kind of order. (The ebook only edition of the complete short fiction of Clifford Simak had the same unprinciple, and I didn’t like it there, either.)
On the other hand, you could get hold of all the volumes and use ISFDb to go through them in your preferred order. The “Collected Poul Anderson” volumes are all available pretty cheaply as ebooks from NESFA, so that’s not as flippant a suggestion as it may seem.
https://www.nesfa.org/press/available-books/?ebooks=e
I’ve often wished for a single volume “Best of Poul Anderson” I could hand to or recommend to people. But The old Pocket Book “Best of PA” didn’t really fit the bill; the DAW “BOOK of PA” was a little closer, but was light on fantasy as I recall. And of course they’ve all been out of print forever.