This is not an entry about raincoats. You can find information on anoraks, the garments, elsewhere. However, in recent times, this same word1 has come to be used to describe not just a coat, but also the type of person who is stereotyped as wearing it.
Anoraks are the sort of people who:
Still live with their mum even though they're in their 30s or older.
Speak Elvish, or Klingon, or both.
So, geeks, basically. Therefore, by extension, that part of the bookshop where you find all that stuff is 'anorak corner'2.
Anorak refers to the slightly socially awkward, detail and trivia obsessed, borderline autistic men (and it is almost always men) who get so into a hobby it takes over their life. It originated with trainspotters, but you can as easily be a football anorak or a Star Trek anorak. However, you're unlikely to hear of a ballet anorak or an opera anorak although you could be an Opera anorak.
Interestingly, 'anorak corner' used to be quite an exclusive little enclave, frequented almost entirely by greasy young men in Iron Maiden t-shirts and the occasional pale girl with long braided hair and a nose stud. But over the last ten years, the influence of Star Trek (the newer incarnations), The X Files, and more than anything else, Buffy the Vampire Slayer, has meant that it is now a lot more socially acceptable to be into this stuff, or at least in that part of the bookshop.