You would get the most out of this book if you had previously studied the Orbis Sensualium Pictus, as the first sections deal with science, the universe, nature, etc. The second part would be easier if you had listened to Taylor's adapted Caesar text, or Lowe's Caesar, if you are a complete beginner.
This reader is unique, in having as a strong focus indirect discourse - right from the beginning, Reynolds starts to introduce it, with imaginary students answering questions on the previous lesson. By the time you reach Caesar, the method of presenting reported speech seems natural.
This is a delightful audiobook. A beginning student, after studying Comenius, will be able to tackle the first half without problems, and after some preliminary study of Caesar, as suggested, the second half will also make for a pleasant experience.
The text can be found at archive.org if you search for 'Reynold's Latin Reader and Nature Study'
Reynold's Nature Study Reader and Novella
4hours 38 minutes of audio