You know A Book Apart! They've published all kinds of iconic books in our field. They are short and to the point. The kind of book you can read in a single flight.
I wrote on not so long ago called Practical SVG. Fortunately for us both, SVG isn't the most fast-moving technology out there, so reading this book now and using what you learn is just as useful now as it ever was.
Better still, now is the time to do it, because 15% of all sales will directly benefit those affected by Hurrican Harvey.