German, English Grammar for Students Of German, 7th Edition

This book describes the basic concepts of German very well and its comparison with English is quite clear and easy to follow. It may be a bit basic if you already have a level B1 or higher but it also serves to remember basic topics that perhaps were forgotten or not seen while learning. The book is also quite short and the size of a normal notebook, so don't expect an A4 book size like the one used in language courses.