A theory of natural philosophy
Isaac Newton's inverse square law of gravitation explained the motion of the solar system very well, but couldn't be used to explain the whole of physics. Boskovich decided that one shouldn't get too enamoured with a simple law, but instead admit a more complicated curve for the force law, deduced from what we see in physics. He proposed that atoms were particles with no size, but that at the smallest scale there was repulsion which prevented them from occupying the same space. At a larger distance there was attraction, to keep solids together. Then more repulsion to explain the dispersion of gases, and then came gravity. Boskovich even thought about repulsion at even greater distances, to explain why the universe didn't collapse to a point - did you really think that there was no idea of a 'cosmological constant' before Einstein?
The book is in three parts. The first introduces his force curve, and justifies his idea of atoms as dimensionless points as opposed to matter as a continuum. He shows how this agrees with the 'Principle of Contiuity' - the idea that there are no sudden changes in physics. The second part deals with mechanics - it has lots of geometrical diagrams. The third part gets on to physics, showing how his ideas can be applied in each of its different areas (it has to be said, of course, that such flexibility comes from the rather vague nature of the force law)
I don't think that many people will want to read the book right through (it isn't that easy to follow), but it's worth knowing about what people were arguing about in the middle of the 18th century, as well as seeing how such ideas fitted in with religion - Boskovich was a Jesuit and had the support of the Catholic Church. There are also some surprisingly modern ideas - such as paragraph 518 where Boskovich mentions the possibility of parallel universes.
Note: This book can be read online at www.archive.org/details/theoryofnaturalp00boscrich