I'm glad to hear you are concerned about what your dc are reading - this is a concern of our family's as well. I think there are many books that are lining shelves of libraries, book stores, and homes, that are simply not good books. We are a conservative family and try to have a similar standard for our dc's free reading time as we do for their homeschooling time, though I must admit the dc's free reading books are not as wonderful as HOD's book picks. I have really struggled with finding books for our dc to read just for free time, and these books don't even have to fit into a specific historical time period, a particular science focus, a certain genre, or an exact age level.

I will say that as dc get older the book selections become more and more difficult to make. We have appreciated Carrie's careful attention in trying to pick the best books possible, but we do not hold her to a perfect standard, for the task at hand is a daunting one, and finding so many books specific to so many things year after year is truly difficult. I have seen Carrie reading with piles, piles, and piles of books around her well into the late night hours, sometimes going through hundreds of books to find 9-12 redeemable ones. It is not easy, and choices do have to be made. Along with these good guidelines you have mentioned...
1. Do the books include boy/girl relationships?
2. Is family life generally valued?
3. Is the language appropriate? (I would not want them to be reading anything that uses bad language repeatedly or takes the Lord's name in vain.)
4. Is violence glorified or overly descriptive?
...HOD also looks for an accurate representation of history, science, etc., and a narrative very well-written living book with a well-formed plot. In general, I'd say boy/girl relationships have completely been avoided so far in HOD, to protect the purity of our dc. A book that has multiple instances of language concerns would never be chosen. If all book choices for a particular focus have been searched out and considered, and a book that best meets all of the qualifications has one or two instances of a language concern, HOD would notify you of this and have you white out the word or cross it off prior to your dc reading it. Family life being valued, specifically the way dc interact with their siblings, parents, and extended family as well as how they behave with elders who deserve respect, is definitely considered. One more consideration is that the worship of idols, false gods, false goddesses, etc. can NOT be glorified, but rather this is seen as pagan, as sinful, and as sad. HOD's plans include ample discussion along with the books being read with Scripture passages, people from the Bible, and Godly character traits to help our dc learn to read with moral discernment, as the only perfect book in this sinful world is the Bible. That is why it is so important not to skip the follow-ups in each of the boxes of plans in HOD - they provide Biblical connections, discussions, analysis, and applications that are key when reading books other than the Bible. Last, HOD works to make sure not to give children an appetite for bloody violence by trying to be mindful of how violence is handled within each book.
Honestly, the book selections narrow as dc mature. The topics become more mature as dc become more mature. This is why HOD's Storytime and DITHOR books always can be replaced with books you would prefer if you've read some and found some better fitting to your family's goals. Trying to find books to represent every genre is a difficult task. Personally, I have - not once - had an issue with the books Carrie has chosen. In fact, I have been delighted as have my dc. I have read a ton of books though, having taught 16 years, and I know how hard it is to find books that fit all of these qualifications. When I look at the book selections of ps and other curriculums offered to families, I have to say I feel very content with HOD's choices.
I think HOD does an outstanding job of choosing books with a balance of all of the above mentioned qualifications, but in the end, it is our responsibility as parents to be sure the books our dc are reading fit with our own personal standards. If you had any concerns with Beyond's titles, you may want to preread the books and choose your own if something arises you are not in agreement with. HOD makes it very easy to replace many books - i.e. DITHOR, Storytime, etc. The history and science books are more difficult to replace, as they are the spines of the program, but I think those are rock solid IMO. HTH!
In Christ,
Julie