yeah, that exactly mirrors my experiences thus far.
What I think is especially interesting about this is how closely it tracks the advice more realistic authors like vonnegut gave at workshops, namely, writing is something you do after you successfully do something else. (he started every workshop by writing "What will you do for a JOB" on the board) By far the best results I've got were by saying to colleagues "Oh, incidentally, I wrote a fiction book that portrays issue X, or features a character who has job/belief system Y", and the best online advertising I've done is through organic facebook and twitter followers (IE just saying "Hey everyone, I wrote a book")
So if you want to sell a book, you need to have lots of friends and colleagues and resources.
or to put it another way: if you want to sell a book, you need to be successful.
I used to do advertising using social media, depressing job because unless you're peddling something that's OBVIOUSLY worth buying (IE quality leather handbags) you don't get a noticeable result. Facebook ads in particular are a borderline scam operation. I can think of almost no time to employ them unless you are actually trying to acquire braindead groupies. THe best analysis I've seen was actually from a science series on youtube:
I also did posters with QR-codes, those have had no effect as well, which is odd because the posters are pretty uh...jarring.