Others have covered this book well here. It is excellent, and I recommend it to scholars and interested practitioners. But it was republished more recently as "The Rebirth of Druidry." They are the same book. So don't buy both, or you'll end up with two copies od the same book.
As with any anthology, the real power of the book lies in the few gems scattered amongst the semi-precious stones of the majority of the writing, and the overall balance and diversity represented by the full cross-section of opinion presented. Carr-Gomm should be saluted for providing commentary from a wide range of authors from organizations outside of his own.
Part I: The Call of the Land was itself worth the price of the book for me. It represents the best of what makes druidism a religion for the future as well as the past.