A good preparation is always useful, for every country, and Lebanon is no exception. In advance, we read Jessica Lee’s Footprint Handbook Lebanon. For someone interested in ancient history, it is quite unpleasant to see that the author confuses Antoninus and Antonius or Alexander Severus and Septimius Severus (to name but two mistakes) but it is a good book.
I also liked Le Liban. De la Préhistoire à l’Antiquité by Guillaume Gernez and Ingrid Périssé-Valéro, which is an archaeological account of the country, with many photos. Had it contained more maps, it would have been perfect, but it was still an extremely useful book. It was recommended to us by the friendly lady of the Librarie El Bourj, a very nice bookshop in the An-Nahar building west of the Place des Martyrs. It has many books on archaeology in stock.