Well if you are after a 'framework' to apply your DM skills to then the
FR books are ideal. I would imagine that Eberron is going to be the same. The realms are huge with a lot of history to explain and the info is contained in 2 books, they are not both full thickness (160 and 288 pages) and they use the
4E lay out and font (meaning both books together have about the content of 1/3 of the mammoth
3E guide, at the most). Therefore you can imagine how much info you get on each area, not much, 2 sides including small incredibly un-detailed map. However they are full of plot hooks (one sentence ones) and give all the high level info you need (gods, etc).
To me they are an ideal mine for ideas or framework for a campaign but very poor if you want to run a campaign with minimal work. If you as a DM were to knock up the same amount of info included in one region of the realms plus the high level stuff for a home brew campaign (for example my favourite campaign start of an Ireland sized island far off the main continent) would only take a couple of evenings work*.
So, in short, if you want the exact opposite of the
3E (and previous) glut of realms lore rulebooks then it is for you.
Or you can use it as an inspiration mine for your own campaign like I do.
*EDIT: Maybe a bit harsh more like 5 evenings.
And yet another word from our sponsors
