They're probably the two most used books if you're doing mechanical/mechatronics/aerospace. You'll be using the statics book in second year, and you'll probably want to refer back to it in third year as well. You'll need the dynamics book for third year too. PDFs or other electronic copies would just piss you off when you're studying with the constant scrolling. Electronic copies are fine for ENGG1000, MATS1101, MMAN2100 etc where the textbooks are less used, but i strongly recommend purchasing these two.