Here are the light novel sales rankings for the first half of the fiscal year of 2012. (Dec 5, 2011 - May 28, 2012)

Volume by volume
*1, 587,891 Biblia Koshoten no Jikentecho vol.1
*2, 446,631 Biblia Koshoten no Jikentecho vol.2
*3, 253,678 Koimonogatari
*4, 249,938 Toaru Majutsu no Index: New Testament vol.3
*5, 220,504 Bokura ga Ita
*6, 200,100 Ore no Imouto ga Konnani Kawaii Wake ga Nai vol.10
*7, 199,950 Toaru Majutsu no Index: New Testament vol.4
*8, 194,649 Baka to Test to Shoukanjuu vol.10
*9, 136,213 Sword Art Online vol.9
10, 132,549 Another vol.1
11, 119,064 Another vol.2
12, 114,266 Hidan no Aria vol.11
13, 104,883 Mahouka Koukou no Rettousei vol.4 Part 2
14, *98,311 Mahouka Koukou no Rettousei vol.5 Part 1
15, *93,281 Seitokai no Ichizon vol.10
16, *92,753 Kotenbu Series vol.1 Hyouka
17, *92,208 Accel World vol.11
18, *90,847 Accel World vol.10
19, *85,575 Full Metal Panic! Another vol.2
20, *85,214 Durarara!! vol.11
21, *83,338 Toshokan Sensou vol.1 Small sized edition
22, *79,249 Boku wa Tomodachi ga Sukunai Anthology
23, *71,008 Mayo Chiki! vol.10
24, *70,951 Highschool DxD vol.11
25, *70,697 Full Metal Panic! Another vol.3
26, *63,673 Highschool DxD vol.12
27, *61,805 Papa no Iukoto wo Kikinasai! vol.9
28, *61,746 Ro-Kyu-Bu! vol.10
29, *60,929 Date A Live vol.4
30, *57,294 Mayo Chiki! vol.11
31, *57,057 Accel World vol.1
32, *54,119 Hentai Ouji to Warawanai Neko vol.5
33, *52,064 Kore wa Zombie Desu ka? vol.9
34, *50,938 Sword Art Online vol.1
35, *49,677 Boku wa Tomodachi ga Sukunai vol.1
36, *49,532 Accel World vol.2
37, *49,495 Papa no Iukoto wo Kikinasai! vol.1
38, *48,237 Chrome Shelled Regios vol.19

Author rankings
*1, 1,034,522 Mikami En ("Biblia Koshoten no Jikentecho")
*2, *,920,087 Kawahara Reki ("Sword Art Online")
*3, *,898,301 Nisio, Isin ("Bakemonogatari")
*4, *,896,547 Arikawa Hiro ("Toshokan Sensou")
*5, *,699,624 Kamachi Kazuma ("Toaru Majutsu no Index: New Testament")

Sources: Oricon, Oricon Youtaiju