This article is from the Amiga FAQ, by Ignaz Kellerer with numerous contributions by others.
The best information available are the RKMs (ROM Kernel Manuals), 3rd edition, by Commodore, published by Addison-Wesley: The Amiga ROM Kernel Manual: Libraries, ISBN 0-201-56774-1 The Amiga ROM Kernel Manual: Devices, ISBN 0-201-56775-X The Amiga ROM Kernel Manual: Includes and Autodocs, ISBN 0-201-56773-3 The Amiga Hardware Manual, ISBN 0-201-56776-8 The Amiga User Interface Style Guide, ISBN 0-201-57757-7
Especially the RKM: Libraries is a must. The RKM: Includes and Autodocs isn't that much worth: Better get the same stuff on disk instead to have it online. See Includes.
AmigaDOS isn't included in these books. The Autodocs give much information, but to go deeper you probably need The AmigaDOS Manual, 3rd Edition, ISBN 0-553-35403-5 published by Bantam Books.
A better choice for developers is The Amiga Guru Book
by Ralph Babel. The book starts with a survey on different aspects of programming the Amiga. (About 250 pages) Useful for beginners are the sections on the Amiga's data types (not to be confused with the 3.x DataTypes used by MultiView, for example), the Includes and the amiga.lib. But even experienced programmers will find useful things here that are missing in the RKMs. But the largest part are about 500 pages on AmigaDOS and, as I think, the most important, because AmigaDOS is the worst officially documented part of the OS. The book is rather concise and hence not as easy to read as the RKMs, but I recommend it as an addition and instead of the AmigaDOS manual. (Not, however, a replacement for the Libraries and Devices, which aren't covered here.) Unfortunately the book has no ISBN and is available in special stores only. But there are some mail order companies which offer it for about 50$ and which accept credit cards:
Almathera Systems Limited Southerton House NBG USA, Inc. Boundary Business Court 482 Holly Avenue 92-94 Church Road St. Paul, MN 55102 Mitcham, Surrey CR4 3TD USA England Voice: +1 (612) 290 9447 Voice: +44 181 687 0040 Fax: +1 (612) 290 9449 Fax: +44 181 687 0490 E-Mail: <firstname.lastname@example.org>
Stefan Ossowskis Schatztruhe Hirsch & Wolf OHG Gesellschaft für Software mbH Mittelstraße 33 Veronikastraße 33 D-56564 Neuwied D-45131 Essen Germany Germany Voice: +49 (2631) 8399-0 Voice: +49 (201) 788778 Fax: +49 (2631) 8399-31 Fax: +49 (201) 798447 E-Mail: <email@example.com>
Someware 27 rue Gabriel Péri 59186 Anor France Voice: +33 27596000 Fax: +33 27595206 E-Mail: <firstname.lastname@example.org> See FAQs.