Starting points to search books:
Even more books available here:
PE -- English Language.
PN -- Literature (General).
PQ 1-3999 -- French Literature.
PQ 4001-5999 -- Italian Literature.
PQ 6001-8929 -- Spanish Literature.
PQ 9000-9999 -- Portugese Literature.
PR -- English Literature.
PS -- American Literature.
PT 1-4897 -- German Literature.
PT 5001-5112 -- Dutch Literature.
PT 6000-6466.36 -- Flemish Literature Since 1830.
PT 6500-6592.36 -- Afrikaans Literature.
PT 7001-7099 -- Scandinavian Literature.
PT 7101-7338 -- Old Norse Literature: Old Icelandic and Old Norwegian
PT 7351-7550 -- Modern Icelandic Literature.
PT 7581-7599 -- Faroese Literature.
PT 7601-8260 -- Danish Literature.
PT 8301-9155 -- Norwegian Literature.
PT 9201-9999 -- Swedish Litearture.
More specific classifications found here