This was a tough book to find information on. I didn't see any copies online.
The author, Angel Day, according to an entry in Wikipedia.org, was an English rhetorician and scholar. This book is his most popular and was very influential.
It is an instructional manual for middle class business people in the late 15th century. There were at least 10 editions. The first edition was published in 1586. It would be the most valuable.
Yours is a sixth edition being published in 1614.
Since I could not find similar books online, it is likely to be valuable depending on condition.
You should take it to a rare book dealer for appraisal.
Here are some URLs for two web pages I used to gather information:
