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 (33 million)
12) R.A. Salvatore (30 million+)
13) Kaoru Kurimoto (28 million)
14) George Orwell (25 million+)
15) Terry Goodkind (25 million)
16) George R.R. Martin (25 million+)
17) Cassandra Clare (24 million)
18 ) Terry Brooks (21 million+)
19) Eoin Colfer (21 million)
20 ) Isaac Asimov (20 million+)
21) Margaret Weis & Tracy Hickman (c. 20 million)
22) Brian Jacquies (c. 20 million)
23) Kazumasa Hirai (c. 20 million)
24) Charlaine Harris (c. 20 million)
25) Frank Herbert (18 million)
26) Hideyuki Kikuchi (18 million)
27) Diana Gabaldon (17 million)
28 ) Douglas Adams (16 million)
29) Kevin J. Anderson (16 million)
30 ) Raymond E. Feist (15 million+)
31) Rick Riordan (15 million)
32) Philip Pullman (15 million)
33) Yoshiki Tanaka (15 million)
34) Stephen Donaldson (10 million)
35) Neil Gaiman (10 million + )
36) Alice Sebold (10 million+)
37) Madeline L'Engle (10 million+)
38 ) Timothy Zahn ( 8 million)
39) David Weber (7 million)
40 ) Laurell K. Hamilton (6 million+)
41) Frank L. Baum (5 million+)
42) Guy Gavriel Kay (3 million)
43) John Ringo (3 million)
44) Joe Abercrombie (3 million)
45) Harry Turtledove (2.5 million)
46) Peter F. Hamilton (2 million+)
47) Dan Abnett (1.2 million+)
48 ) Robin Hobb (1 million+)
49) David Gemmell (1 million+)
50 ) Steven Erikson (1 million+)
51) Trudi Canavan (1 million+)
52) Chris Wooding (450,000+)
53) R. Scott Bakker (125,000+)