G1, your parents as G2, I now have a complete tree for me to G5. You might think, hey, cool, that means you have your kids to G6, but there's a hole in R.'s G4, 4 holes in G5.
When I was quite young, I got a copy of a genealogy for my maternal grandfather's branch of the family (the compilation closed after my younger sister was born, so we're all in it, even). While I've been poking at it periodically ever since, it is only as I'm laboriously entering information from it and from the genealogy I got when I was 20 for my paternal grandmother's mother's branch, that I'm starting to see what _is not_ included.
Yesterday, at the library, I was looking around in HeritageQuestOnline (have access from home via the library card, now that I know it exists and is useful), and that got me a 1954 published genealogy for the Poages, which are a few generations back in my maternal grandmother's line (and I have a very solid connector between us and it, so this isn't shady at all, as are attempts that I make to use Terrill genealogies, a branch off the same part of my tree). I also looked at several genealogies for my last name (a very common name), predictably unable to connect them to me. It was interesting, however, to flip through a lot of instances of the genealogical genre. Of the two I "grew up with", one is a "family register": just the facts, ma'am, with a very, very short introduction that nevertheless turns out to be important. When a "family register" talks about how most of the family continues in the simple faith of the ancestor, you should not be surprised if entire chunks are missing because someone rather conspicuously left the group at some point. I could speculate as to why we were included, but I think I will not at present.
The other has a lot of stories in it, and that turns out to be not at all uncommon in the genealogical genre. Also, a heavy religious tone isn't at all unusual, either.
Divorce records are often difficult to find compared to birth/death/marriage records, and not knowing there were more marriages can really mess with efforts to find a death record. Genealogies, especially ones that take a more adulatory tone to ancestors, have extra motives for conveniently leaving out any divorces they did trip over. In a very conspicuous instance, the P. genealogy I got when I was 20 leaves out any vital statistic for my great-grandfather beyond his marriage to my great-grandmother. I didn't even go looking for marriages beyond the first one until my cousin told me there was a divorce. I _really_ didn't expect to find 3 more marriages and 1 more divorce.
It's clear, from my readers' kind and helpful responses, that we would like it better if more complete information was included in a genealogical work, including the compiler's (explicit, clearly labeled) opinions. Because the process has been so much of the interest for me, I will inevitably include that as well (also a traditional component of the genre).
My current sense of what I might produce depends on whether I think of this as a linear narrative incorporating all the information, or as a short narrative with substantial appendices, or as a cluster of stories with connections. If I do this as a web-only (the way my parenting work is constructed), that last is very tempting. I think I do see some value in a process-oriented linear narrative that captures the iterative nature of the work. That is, I started out knowing who my grandparents were, and some of my great grandparents, all of my cousins and some of my parents cousins. Each step of entering what I knew suggested possible additions, and investigating stories (grandpa came over after a brother named Harry who wasn't really named Harry; Harry's daughter married a man name Harry A., but we don't know her given name(s)) produced more additions. Carried through to the present, each additional connection produced more distant cousins who could be found on facebook and, through correspondence, the process repeated (more names, more stories, more avenues of research).
While not easy to explain briefly, the learning curve is surprisingly like a facebook game: so gentle as to be almost imperceptible, until you compare what you do now to what you once did, or you watch someone else starting out. Only then do you realize how able you have become, all unconsciously.