This was one of the major texts recommended to me when I first began to study algae, and it was old then. (I believe it first came out in 1982.) Often science books, particularly textbooks, become obsolete quite quickly but I've just read this again and it's as useful as it ever was, which was very. It's so useful because it's not cutting edge. I mean yes, Dring was using the most up-to-date studies available at the time when he wrote it, but this is a general, introductory text that covers all the phycological basics - for instance seaweed zonation and geographical distribution - and this is the stuff that essentially doesn't change. It's also very clearly written (at least mostly, the chapter on photosynthesis is less accessible than the others) and full of tables, figures, and illustrations to make things easier on the reader. All in all, an extremely useful reference text, even though it's closing in on 40 years since its first publication.