Perhaps the first major book with the theme of 'Natural History' was by Pliny the Elder. It's certainly the earliest to survive - there are many important books lost to events in the past.
You can read about the work here.
The largest single work to have survived from the Roman Empire to the modern day, the Natural History compiles information gleaned from other ancient authors. Despite the work's title, its subject area is not limited to what is today understood by natural history; Pliny himself defines his scope as "the natural world, or life". It is encyclopedic in scope, but its structure is not like that of a modern encyclopedia. It is the only work by Pliny to have survived, and the last that he published. He published the first 10 books in AD 77, but had not made a final revision of the remainder at the time of his death during the AD 79 eruption of Vesuvius. The rest was published posthumously by Pliny's nephew, Pliny the Younger.The book can be read online in full here.
Image: a 1499 copy of the book
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