"RTFM" is an old saying: Read The "Fine" Manual. Sun still sells printed manuals, but doesn't automatically distribute them. As with all real UNIX systems, you do get a full set of online "man" pages. A smaller, lighter, bookshelf-friendly :-) set of CDROMs called "The AnswerBook"(tm) contains all the printed documents in machine-readable (PostScript) form, with hypertext capabilities and a keyword search engine. 90% of your introductory questions are answered therein!
In Solaris 2.x the Answerbook set gets increasingly more divided into pieces. It is currently split over a number of CDs, currently (2.5.1):
Solaris 2.x CD: Solaris 2.x User AnswerBookSolaris Desktop 1.x Wabi 2.x Answerbook Solaris Common Desktop Environment AnswerBook 1.0.x
Updates for Solaris Operating Environment 2.x Solaris 2.x on Sun Hardware Answerbook
Server Supplement NSKit 1.2 answerbook Solaris 2.x System Administrator AnswerBook (Solaris 2.5.1 Supplemental System Admin AnswerBook) Solaris 2.x Reference Manual AnswerBook
Solstice AutoClient & AdminSuite Solstice AutoClient 2.0 AnswerBook Solstice AdminSuite 2.2 AnswerBook
Solstice Online Disksuite DiskSuite 4.0 AnswerBook
Solstice Backup Solstice Backup 4.2 AnswerBook
Solaris 2.x Software Developer Kit All programming manuals.
Solaris 2.x Driver Developer Kit Device driver developer manuals.
Only the first two CDs ship with the desktop edition, the third is SPARC specific. The last two CDs are part of two separate products; the SDK and DDK. The rest is server only, though the reference manuals are available in nroff source form.
There is some overlap between CDs.
As distributed with 2.1 and 2.2, the Answerbook search engine runs only with the OpenWindows ("xnews") server, not with MIT X11.
In Solaris 2.3 through 2.5.1 answerbook uses X extension DPS. If you are using the MIT server instead of what Sun provides, you'll have to use one of several "answerbook workaround" scripts that are in circulation. The AnswerBook distributed with 2.3 and later runs with the OW3.3 X11R5+DPS server, so it should display on any X11+DPS server, such as on DEC, IBM and SGI workstations.
In Solaris 2.6, answerbooks are distributed in SGML format; they are presented through a special web server which is also able to convert old Postscript answerbooks to HTML on the fly. Sun has a site on the web that has many of the answerbooks available.
Following a link at that site, you can order hardcopy from fatbrain.com or download PDF books for printing or viewing.
You should buy (or print from within Answerbook) at least the reference manual and the System and Network Administration books, because if your system becomes disabled you won't be able to run the Answerbook to find out how to fix it...