Reading book for 6-7-8 yrs old

[Arkadia]

I know questions like this have been posted before, but here we are.
I am looking for advice on books to get for my DD2 (which could read my DD1 too). DD1 is 8,5 and DD2 is 6.
Reading ability not an issue, so no need for anything Biff-and-Chip-like. I would avoid Dhal as well because I don't enjoy it that much.

The "problem" we have at the moment is that DD2 is getting books that are too difficult to understand (we are finishing now Deathwood Letters, which I think is fantastic, but way too difficult to fully understand). Recently we have read "Lost and found" (very good indeed) which I found was more approachable. Also "The gift from Winklesea" (which seemed harder).
So, I am looking for some kind of chapter book which is a good read, but it is approachable for a younger audience, without looking too childish.
For example, the Princess in Black probably fits the bill. It is VERY easy to read and it is not complex to understand (alas, we have run out now. I particularly recommend the first one), but still has some kind of structure.

Our library sounds similar. DS will gravitate to series he knows e.g. Beast Quest despite having outgrown them now. He would be lost in the masses of books whose titles/authors mean nothing to him, and the majority of which are too 'old' for him anyway; wouldn't know where to start.

When preschooler DD isn't with us, I do as Irvine suggests - look through the books, pick some out and pass to DS to read the blurb and decide if it sounds interesting.

Thing is, for me to be able to do that reasonably efficiently, I need to myself have an awareness of what I might be looking for. Hence threads with suggestions, like this one, are very useful for me.