Hello Aspirant,Hope you are doing well

String theory is an attempt to describe all particles and all forces in nature in one unified theoretical framework. It encompasses quantum mechanics and gravity, and it is based on the idea that the fundamental building blocks of matter are not particles, but strings: objects which have some length, and which can vibrate in different ways.

Some of the best books were

• Superstring Theory (1987), by Green, Schwarz and Witten. This is a two-volume, massive 1000 page treatment of the quantization of the superstring and ideas about Calabi-Yau compactifications dating from right after the First Superstring Revolution in 1984.
• String Theory (1998), by Polchinski. In two volumes and 900 pages this covers most of what is in Green-Schwarz-Witten, while also surveying D-branes, the second Superstring Revolution, and much of what was learned about string theory during the decade after GSW.
• A First Course in String Theory (2004), by Zwiebach. This is the textbook for an undergraduate course, so is at a lower level than the other two books.

Hope this helps you

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