Eero Einar Book (1910 – 1990) was a Finnish chess player and engineer.

A six-times Finnish champion who represented his country six times in the Chess Olympiad, he was awarded the International Master title in 1950 and became an honorary Grandmaster in 1984. His significant international tournament victory was a tie for first place with Gösta Stoltz in the 1947 Nordic Championship in Helsinki.

He played many of the world's top players, and had a plus record against Max Euwe and Miguel Najdorf. He beat Euwe with black pieces in Dubrovnik in 1950 (moves given in Algebraic chess notation):

1. Nf3 Nf6 2. g3 g6 3. Bg2 Bg7 4. c4 O-O 5. O-O d5 6. d4 e6 7. b3 b6 8. Ba3 Re8 9. Nbd2 Bb7 10. Rc1 Nbd7 11. Re1 Ne4 12. Qc2 Rc8 13. Rcd1 f5 14. Bb2 Qe7 15. Ne5 Nxe5 16. dxe5 Red8 17. Nb1 dxc4 18. Qxc4 c5 19. f3 Ng5 20. Na3 a6 21. Qh4 b5 22. Rd6 Bf8 23. Bc1 Nf7 24. Qxe7 Bxe7 25. Rxe6 Rc7 26. f4 Bc8 27. Rb6 c4 28. Rb8 Bc5+ 29. e3 Bb4 30. Rf1 cxb3 31. axb3 Be6 32. Rb6 Bc8 33. Rc6 Rxc6 34. Bxc6 Be6 35. Nc2 Bc3 36. e4 Bxb3 37. Ne3 fxe4 38. Bxe4 a5 39. Rf3 b4 40. Nf1 a4 0-1

He also beat Paul Keres in the 1952 Helsinki Olympiad.