“Numerische Mathematik” from Hans-Rudolf Schwarz and Norbert Köckler, is a very good book about numerical computation algorithms. For me a standard compendium and I can recommend it to both groups, beginners and experts. Unfortunately, I think, it’s only available in German.
There is not much to say about “The C++ Programming Language” from Bjarne Stroustrup. It is simply the standard book every C++ developer should have read.
“REST und HTTP” from Stefan Tilkov, Martin Eigenbrodt, Silvia Schreier and Oliver Wolf is a extrem good book about design and building clean REST interfaces.