Microelectronic circuits by Adel Sedra and Kenneth C. Smith
Introduction to Linear Algebra by Gilbert Strang
In case you want to learn Engineering Electromagnetics, great textbook by William Hayt and John Buck
Haven't yet read any other awesome basic textbook on 'Computer Networks' like the one by Andrew S. Tanenbaum
'Digital Signal Processing' by Oppenheim and Schafer
Although these are not textbooks but among other good reads are 'Crossing the Chasm' by Geoffrey Moore, 'The Innovators Dilema' by C. M. Christensen, give amazing insights.