There are some books that I periodically re-read, and this book is one of them. It also happens to one of the first books that I brought on my own after leaving home (back in the stone age before ereaders and the internet in every home).
The Ivanhoe Gambit is the first book in the Time Wars series. Set in an universe where time travel has been discovered, Hawke uses famous stories of fiction (such as Ivanhoe and Robin Hood) as historical events. In the case of this book, I have never read the original version of the Ivanhoe story, but I am familiar with the history of the Crusades (more so now than when I first read this novel).
One of the reasons that I like this novel is that it is a good example of the literary equivalent of a television pilot--the hook that sells the rest of the series--one that could have stood alone if necessary. One of the frustrating things about the way that the print market was set up was the fact that a book series lived or died based on the sales of the first book (just like TV decides based on the number of eyeballs that watch a pilot episode); during the 1980s, there were several science fiction series that had only the very first book published. A couple of the series I loved based solely on their initial books, despite the fact that none of the rest of the series were issued...or maybe even written.
And one of the frustrating things about such failed literary series (provided that you are willing to admit science fiction into the literary world) was the number of loose ends that some of those first books left dangling. This is not the case with The Ivanhoe Gambit; outside of one loose end, and it can be read as an actual closure of a loose thread if one pays the "what if no more of the series was published," the book is self-enclosed. One can read this book as a stand-alone book. As such, this book is many ways, my model for what first book in a series should be like.
Given the fact that I have read this book a dozen times (at least), it should be no surprise that I give it five stars.
[Disclosure: I paid a whole dollar and some sales tax in 1985 to buy an used copy of this book--a copy that I still own.]