A pdf version of the latest edition (6th) of the classic textbook by Robert D. Cooter and Thomas Ulen has been generously posted online and is available for free download here.
Interestingly, the authors announced that they intend the textbook to become a living document with incremental changes, updates and supporting materials to follow continuously:
Looking forward to next year, this duet will become an internet symphony that takes full advantage of the internet revolution in publishing. Improvements will be posted to the internet continuously in small amounts (7.1, 7.2, 7.3, etc.), until a new edition appears with large changes (8.0). Not just a textbook, the 7th edition will have supporting materials, including translations. For updates, join the email list as indicated above. Perhaps you will have something to contribute to the website. For the best feast, the host supplies the main course each guest contributes a dish.