His chapter on the Maltese islands cart grooves is a very good summing up of all the evidence and the reasons why the cart ruts on Malta were not built for transportation and why most modern ideas are wrong. Since he wrote the book there have been some developments in cart ruts information, especially about them being found around the Mediterranean and the world, although not in the numbers found on Malta and Gozo.
Daniken suggests that the megalithic temples and cart ruts were built as a sign of worship or admiration to the Maltese gods. That the old Gods of man who lived amongst us, for example perhaps the giants like the Nephalim mentioned in the Bible, may have helped man construct the massive stone buildings and ruts, perhaps using techniques that were not necessarily available to ancient man.
If you are interested in the more exotic theories that are linked to the reason of why Malta’s cart ruts were created, then Erich von Daniken’s book and ideas could be worth a good read.
Daniken certainly asks awkward questions which standard peer reviewed based explanations may not have been able to explain, perhaps the academic The Significance of Cart-Ruts in Ancient Landscapes book might now be able to answer.