Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses
Publisher:
Jo. Martyn and Ja. Allestry
Year:
1665
Available online in multiple formats at Project Gutenberg
This book inspired Leeuwenhoek. His first letter to the Royal Society repeated and extended some of Hooke's observations.
Hooke himself drew the wonderful illustrations. Many of the observations were made with a 40x microscope that Hooke got from Christopher Cock, London.