Gross. I hate seeing Prima guides on the main page. It makes Steam feel tacky to me for some reason. I guess because I only ever see Prima guides in dirty used game shops.
This also clutters up searches and stuff now. If you type Splinter Cell into the search box, you'll have to sift out the games from the Strategy guide.
They would be better off without this feature in my opinion.

http://store.steampowered.com/app/22805/
"Easy Website Access: Official strategy website is fully searchable, 100% developer approved content and accessible from the in-game overlay and from your account."
It looks like these aren't even e-books. They're web pages you get access to if you pay...

The new was not there when i posted. Seem they did things well for integration. But one question remains. Will you be able to open a guide for, say DAO, in the overlay while playing a RETAIL copy ? Or can you only see the guide in overlay when you game was bought from steam ?

They are in PDF format and they have some kind of DRM.

Tried that. Steam overlay doesn't work on retail, so added the installed retail game to Steam. The guide button doesn't appear. So as of now, the answer is no.
The guides where you have the Steam game too, get an guide button on the actual game page. So you can access that with the overlay. However, right now I don't see where they put a guide that you don't have the game from Steam and didn't install right after purchase. They don't appear in your game library.
So it seems they put a lot of effort in to getting it right, but didn't thought it to the end - that or it's already too late for me to see the obvious which I'm missing right now. :)

different topic... I'm somewhat confused today

It is kind of silly to buy a walkthrough considering GameFAQs... you know... exists.
I always thought Prima should go more towards the "making of" kind of book, with behind the scenes stuff dominating the book, rather than being possibly tacked-on at the end. Each "making of" could also include a walkthrough and such.

No, the ones on Steam are web pages. Prima does both "eGuide" and "Website" versions for various games, but from a quick glance it looks like all the ones on Steam are the website type.

Yes and no.
Yes - of course each and every Guide sold, printed or in digital form, is somewhat questionable. Nobody really needs them, almost all information is somewhere available for free on the net.
No - having 5 or more different tabs open in your browser to getting access to all the info you need right now for a game.... sounds familiar? It's inconvenient, takes more time then necessary scanning for a specific part, and never really complete. For example: there are over 300 dungeons / places in Oblivion without any quests. Try getting information on them...
Call me nuts, but I've always been a sucker for those guides. Be it for Might & Magic 3, Ultima 7, my treasured Morrowind Prophecies or Fallout 3 - I honestly can say my gaming experience wouldn't have been the same without those. GameFAQs (which I love and use on a regularly basis) hasn't and can't change that.
And as far as "making of" goes. With gametrailers, youtube and the like, I feel this section is about equally covered.

GameFAQs is hampered by the way it deals with multimedia, though (or rather, the way it doesn't). It's great for discussing RPG character builds or how to breed a black chocobo, but not so great for many modern 3D games.
For example, the attached screenshot is useful (source) in the unlikely event that you ever get stuck in Max Payne.
This does not translate well to text. "Go into the next room and jump on the crates up to the conveyor". Which room? Which crates? What's the conveyor?
A quick look at the screenshots for some of those guides is disturbing, though. I remember when a lot of that information used to be in the manual.

If you think $10 to access a web guide is a poor deal, on Prima's own site the guides aren't discounted--that's a full $20 per guide.
GameFAQs does support HTML guides, oddly enough--complete with images and whatnot--but there are some noticeable layout restrictions with even this system and there is no online editor whatsoever, so unless you know HTML or find a good web design program this isn't a very accessible option. As you'd expect it hasn't been particularly successful and there are only a handful of HTML guides despite this being an option for a while now.
GameFAQs' various shortcomings have led to the development of sites such as StrategyWiki, which attempt to bring walkthroughs into the current age using multi-editor wiki implementations and whatnot, but it will be a very long time before any of them can wrest any sizeable market away from GameFAQs.

I'm not surprised Steam are selling them now. Both D2D and GamersGate have been selling Prima guides for some time. Of course Valve want a part of that pie.

Guides are another example of the industry scamming us into spending more money.
20 years ago, manuals were thicker and contained more info. You'd find a backstory, game mechanics, descriptions, etc. in the manual and often you had several manuals too: one with the game mechanics, one with the technical references (which would be system-dependant) and one with the units or maps/.
These days you got a very thin 20-30 page manual of which half is legal blabber & credits. You get the completely useless basic mechanics (click there to open that, move your cursor there to move the camera) which any normal person figures out on his own but all the vital info on what a certain button actually DOES or what a special power of a unit can DO, is absent.
And what a coincidence there's a licensed hint book available which is more a manual than a hint book! Charging you $10+ for what you should mostly have gotten for free! When you need a hint book to know what certain potions do or to discover how a certain spell works, it's gone too far, full stop.

I've always liked to have an official printe dguide to a game I own, kind of makes it seem like you've got the whole package then. Guides are mostly useful for RPGs however. I once bought a guide in a mad moment for Halo 3 on its release night. WTF ?. When I came to my senses a few days later I could've kicked myself.
However, a strategy guide for a game like Might & Magic 6 or Two Worlds is a massive advantage

I really don't see the point in digital guides.
If i want to buya guide, it is because i want something physical to have on my lap, desk or hands. A digital guide lacks this which can cause problems with switching between the guide and the game as i find some games can bug out or crash with alt+tabbing.
If i want to actually have something physical, i have to dedicate my own resources to printing off the guide myself, and even then it's no where near the quality of a proper physical guide.