Recommendations for books on string theory include "A First Course in String Theory" by Barton Zwiebach, which is well-suited for physics students with a background in special relativity, basic quantum mechanics, electromagnetism, and introductory statistical physics. The book is praised for its accessibility and engaging writing style. For those with a more advanced understanding, "String Theory and M-Theory: A Modern Introduction" by Katrin Becker, Melanie Becker, and John H. Schwarz is suggested, requiring familiarity with quantum field theory, general relativity, and a solid mathematical background. The discussion emphasizes the importance of these texts for students preparing for advanced studies in theoretical physics, particularly in the context of training courses and thesis work.