Think this would be a good thread to get going as I've only recently made some discoveries that were very helpful & new suggestions are definitely welcome. Obviously there is the strandard https://www.amazon.com/dp/0750628960/?tag=pfamazon01-20 but what else it there hidden away that isn't mentioned in nearly every thread on physicsforums asking for book recommendations? Well, first off I found this amazing 10 volume course on theoretical physics by Walter Greiner that simply looks astonishing! Browsing around I found this basically unmentioned two-part tome on classical mechanics by https://www.amazon.com/dp/0471091448/?tag=pfamazon01-20 which I found in my library and the contents are superb. This should be read by every undergraduate as far as I can ascertain from reading it. Another discovery is https://www.amazon.com/dp/0126546703/?tag=pfamazon01-20 5 volume course on theoretical physics In England there is a whole course published called the Manchester Physics Series that has barely been mentioned on here I think people would find interesting. Of course there are two seperate M.I.T. Berkeley Physics Series by https://www.amazon.com/dp/0393099709/?tag=pfamazon01-20. https://www.amazon.com/dp/013805326X/?tag=pfamazon01-20 could also be considered a series. As for mathematics I would call Serge Lang, Michael Spivak, Richard Courant & Tom Apostol all a series. So, let the rare and unmentioned recommendations fly in!