Otoh, when landing in OAK, one can see a big network of dirt roads. It is just that they are not in a particularly interesting area so you may have to "discover" them for yourself.
Generally, better for Subarus is the Massey series of books, including his California book (one for south and another for north). Unfortunately, the Cal books are so old for 4wd guides (like close to 20 yo) that they are only useful as a first step rather than an actual guide. Who knows how many of those trails have drastically changed and how many have been closed.