| A Calculus of Angels | |
| Author: | Gregory Keyes |
| Cover Artist: | Therese Nielsen |
| Country: | United States |
| Language: | English |
| Series: | The Age of Unreason |
| Genre: | Alternate history, fantasy |
| Publisher: | Del Rey |
| Release Date: | March 30, 1999 |
| Media Type: | Print (Paperback) |
| Pages: | 406 |
| Isbn: | 978-0-345-40607-1 |
| Dewey: | 813/.54 21 |
| Congress: | PS3561.E79 C35 1999 |
| Oclc: | 39695456 |
| Preceded By: | Newton's Cannon |
| Followed By: | Empire of Unreason |
A Calculus of Angels is an alternate history and fantasy novel by American writer Gregory Keyes, the second book in The Age of Unreason series.[1] [2] It was initially published by Del Rey on March 30, 1999. A follow-up to Newton's Cannon, the book is set in 1722 and continues the alternate history where Isaac Newton discovers that alchemy works, and a powerful science is built upon it.