Full details at the link, but the quick version is as follows:

If an author is not present, that's likely because official sales figures have not been released yet. Brandon Sanderson and Patrick Rothfuss, for example, should definitely be on here but as they have no official figures, I can't place them. That's also true for older authors like Arthur C. Clarke and Philip K. Dick.

1) J.K. Rowling (c. 450 million)
2) Stephen King (c. 350 million)
3) JRR Tolkien (c. 300 million)
4) CS Lewis (120 million+)
5) Stephanie Meyer (116 million)
6) Anne Rice (100 million)
7) Robert Jordan ( 80 million+)
8 ) Sir Terry Pratchett (75 million+)
9) Richard Adams (50 million+)
10 ) Suzanne Collins (50 million+)
11) Christopher Paolini (39 million)
12) Stanislaw Lem (30 million+)
13) R.A. Salvatore (30 million+)
14) Kaoru Kurimoto (28 million)
15) Terry Brooks (26.5 million)
16) George Orwell (25 million+)
17) Terry Goodkind (25 million+)
18 ) George R.R. Martin (25 million+)
19) Cassandra Clare (24 million)
20 ) Kevin J. Anderson (23 million)
21) Eoin Colfer (21 million)
22) Isaac Asimov (20 million+)
23) Margaret Weis & Tracy Hickman (c. 20 million)
24) Brian Jacques (c. 20 million)
25) Kazumasa Hirai (c. 20 million)
26) Charlaine Harris (c. 20 million)
27) Raymond E. Feist (20 million+)
28 ) Frank Herbert (18 million)
29) Hideyuki Kikuchi (18 million)
30 ) Diana Gabaldon (17 million)
31) Douglas Adams (16 million)
32) Michael Ende (16 million)
33) Rick Riordan (15 million)
34) Philip Pullman (15 million)
35) Yoshiki Tanaka (15 million)
36) Timothy Zahn (15 million)
37) Robert Heinlein (11.5 million)
38 ) Stephen Donaldson (10 million)
39) Neil Gaiman (10 million + )
40 ) Alice Sebold (10 million+)
41) Madeline L'Engle (10 million+)
42) David Weber (7 million)
43) Laurell K. Hamilton (6 million+)
44) Frank L. Baum (5 million+)
45) Ursula K. Le Guin (3 million+)
46) Guy Gavriel Kay (3 million)
47) John Ringo (3 million)
48 ) Joe Abercrombie (3 million)
49) Margaret Atwood (3 million+)
50 ) Harry Turtledove (2.5 million)
51) Max Brooks (2.4 million+)
52) Sergei Lukyanenko (2 million+)
53) Peter F. Hamilton (2 million+)
54) Brent Weeks (2 million)
55) Andrzej Sapkowski (2 million+)
56) Lois McMaster Bujold (2 million)
57) Dan Abnett (1.2 million+)
58 ) Anne McCaffrey (1 million+)
59) Robin Hobb (1 million+)
60 ) David Gemmell (1 million+)
61) Steven Erikson (1 million+)
62) Alastair Reynolds (1 million+)
63) Trudi Canavan (1 million+)
64) Chris Wooding (750,000+)
65) Hugh Howey (500,000+)
66) Alison Croggon (500,000+)
67) Lynn Flewelling (350,000)
68 ) Peter V. Brett (310,000+)
69) Mark Lawrence (250,000+)
70 ) Michael J. Sullivan (250,000+)
71) Karen Miller (250,000+)
72) Scott Lynch (145,000+)
73) R. Scott Bakker (125,000+)
74) Elizabeth Moon (100,000+)
75) Gail Z. Martin (100,000+)