I read many technical books as ebooks (epub or pdf), but these are primarily about "current tech" that will most probably become obsolete in 2-3 years. But I bu

I read many technical books as ebooks (epub or pdf), but these are primarily about "current tech" that will most probably become obsolete in 2-3 years. But I buy real books for more fundamental technical areas, where the information will be relevant for a long time. Another factor is if the book is math heavy - around deep learning & related topics, although in many cases PDFs are ok.