For some reason I've noticed that Familia Romana (LLPSI Book 1) gets talked about a lot, but I can barely find anything about book 2 (Roma Aeterna). To me, that book was exceedingly helpful in moving from practice textbook sentences to being able to tackle actual Roman authors, both in terms of developing vocabulary (earlier when I tried reading De Bello Gallico I had to look up so many of the words that it simply was not a fun experience) and some of the more advanced grammar subtleties that aren't covered in basic textbooks. It was also good for just those little confusing things that you might find in a Latin text (things like "quod si" meaning "but if", or "passuum" being sometimes eliminated in "milia pasuum") and overall just a very good book. Having read it I was able to proceed through DBG with barely any need to consult a translation, a far cry from my initial, laborous attempts! So if you are at that same state, I highly recommend it!