The original King’s Quest largely fits your criteria.

You can visit the vast majority of areas from the beginning. There are a few places (such as a cave, etc.) that you can’t get inside until you do something first, and there is one section of the “world” that you can’t visit until the latter part of the game, but those are the minority.

Many puzzles in the game can be started in whatever order you choose – although many puzzles will require you to complete another puzzle first to obtain a necessary item. But you can at least start (or be aware of) many of the puzzles right from the beginning – and then go off to find a way to solve them in whatever order you want.

Combat is essentially non-existent, and the protagonist has no stats or ability scores of any kind.

I haven’t played the other games in the King’s Quest series, so I’m not sure if they still fit these descriptions.

Since the game is telling a story, they can't let you get too far out
of sequence or the story will make no sense.

Most adventure game are like a book, but with the chapter's pages glued together..
Some game you can skip around to each chapter heading,
but you can not look at the pages inside the chapters.

Some adventure games, the whole book's page are glued together,
excepting for the opening page....before the popularity of the internet,
we called it being "stuck"

Depends... if it's your task to actually piece the story together...

That reminds me - what of classic "whodunnit" settings in the vein of Agatha Christie?

Cruise for a Corpse and Murder on the Mississippi would actually fill the requirements nicely. You can visit most locations any time (ok you need to find some keys to unlock certain cabins) and talk to people and examine stuff to gather clues. At least the first should really be on GOG btw.
Are there more modern games following this formula?

Another candidate would be The Last Express - but this one also has action scenes and AFAIK not all of them can be avoided.

As I said, an adventure game that does not borrow aspects from other genres.

Even some Mario game has been advertised as "adventure game" in the past. Or Zelda. ;-)

I think whoever classified those games doesn't really understand what "adventure" really means in this sense.

Zelda does have more claim to being in the Adventure category, given the exploration aspect and (particularly in Link's Awakening) the nature of many of the puzzles you have to solve (the Ocarina of Time puzzle where, in the Deku Tree, you have to figure out how to get past the thing that prevents you from falling to the lower levels is an excmple here). With that said, they are still definitely not pure adventure games.

La-Mulana, while not pure, definitely deserives the "adventure" categorization; other Metroidvanias might not.

I rather think the console world - for lack of the "adventure" genre that home computers provided - simply had their own definition of "adventure game" at the time.
The genre name on computers comes from tradition: (Colossal Cave) Adventure. But if you think of adventure movies or book - there's plenty of action and stuff - so games like Uncharted, Tomb Raider or even many RPGs would actually fit the description better than, let's say, Maniax Mansion.

Well... early Sierra adventures where mentioned and came to mind for me as kind of close too. The SQ, KQ, LSL trinity. At least up till they replaced text with point and click; felt a tad more restricted after that then; but not by much. 'cept KQ5; this still felt fairly open. At least as far as it makes sense for traditional adventures. But my mind might play tricks on me here; outside a SQ3 nostalgia romp 1-2y ago I have not touched adventure games for decades (at least not really played them).

Oblivion/FO3/FONV open worldliness minus any combat, treasure hunt exploring and lack of other RPG features does not sound like something entertaining.

You could still have treasures to hunt for. Said treasures could either:
* Be used to solve puzzles (which need not have unique solutions)
* Provide extra points (many older adventure games give you a score; finding treasures could be one way to increase that)

Kind of fits the Sierra adventures. They all have a score and I think I have not managed to have one of them full after having finished the games :)

But if it i.e. an Oblivion without any RPG & combat features is you seek: no idea, sorry. :(

I disagree with that quite strongly. Based on the fact that at its most entertaining or thrilling, my life has been pretty "open world", yet features no physical fights, and barely any stats increase.

But also, if you look at all the action adventure movies around : actual fights don't necessarily take a huge place in them (compared to games : even violent action movies feature less fights and more diverse action than the non-stop shooting of their videogames adaptations). And the fights are not often the most interesting aspects of the experience. You could easily have a point and click version of Die Hard. Or an open world Indiana Jones (not too different from Gabriel Knight 3, maybe).

Which reminds me : sleuth games are often an exemple of open world adventuring.

Your stats in "writing; English" is now considerably higher than a day after you birth. ;)

Unless you're Cylon! O.O

I do get the general gist of what you are telling though; but I'm not sure we are envisioning the same thing. I probably removed a few features too much.

Also coming to mind: Zak McKracken often allows you to travel freely (if you can afford it...) and tackle the various puzzles around the world in any order. That's of course only in some stages of the game.

Who says the game is telling a story? Maybe that's *not* the point of the particular adventure game in question. Maybe the game is all about exploration and discovery?

(Random thought: What if a pure adventure game *didn't* have an ending; you just continue playing until you max your score or get bored?)

I can imagine open world adventure games to be fun, but I think they'd be pretty hard to pull off, requiring a lot of resources and pretty good writers. If story-telling is the main focus, the story or stories would have to be really engaging, but at the same time they would require a different kind of story-telling than what you'd find in most other adventures and videogames, due to the non-linearity and open world. So far, the games with good stories are rarely non-linear, and open world games seldom have gripping stories. I would be interested in such an experiment, bit it's sound quite complicated, expensive and risky.