I’ve borrowed the fifth edition of this title from the library so many times that it might as well be a part of my personal collection. When I learnt that a sixth edition was to be released, I knew I had to buy it. (Incidentally, the publisher Routledge sells it on their site and there was a Boxing Day sale at the time.)
There have been a few changes from the previous edition. In particular, the addition of advice for speakers of Romance languages is welcome. As a francophone, learning Spanish has been easier in some respects; but Spanish is very much its own language and mistakenly importing grammatical concepts from French has led to negative interference, in my case. The authors did an excellent job of indicating where these bifurcations occur.
Also welcome was the addition of examples from Latin America. Though this is an English book focusing, rightly, on peninsular Spanish, one cannot dispute the importance of Latin America on Spanish today. The previous edition did have several Mexican examples, but the authors did a great job of adding examples from the Southern Cone (for which I am delighted as I’m learning the Rioplatense dialect).
This is the most comprehensive - and well written - reference on Spanish grammar. I highly recommend this book to anyone learning Spanish, irrespective of the dialect one chooses to learn.