Set their expectations on what you can and cannot do straight.
I remember the same thing from my first D&D session. We were walking along, chatting amongst ourselves, when we came across a cow. Since that was one of the first things we, as players, encountered in that world, we bombarded the cow with skill checks and wasted like 15 minutes. In the end, it was just a regular goddamn cow (who would have guessed ^^).
Ultimately, we learned from this encounter (and various others in the first few sessions) that not everything is mysterious just because the DM mentioned it.
Where is your players' behavior coming from?
Concerning your players: The first thing we need to figure out is why they focus so much on details. Is it like in the example above, that they simply think that because you mentioned it, it has to be important? Or is it something else?
The way I see it, however, is two-fold. On one hand, I'm gonna go out on a limb here and say that your players came to pen & paper from video games (or behave like someone who does), and as a consequence, they have unrealistic expectations on what you can and cannot do.
Your players are behaving like they are used to behave in video games.
First of all, your players seem to be highly focused on looting, indicated by the fact that they're pissed when they want to loot the ruin but there's nothing there. This is directly related to their (supposed) video gaming background I mentioned above.
More precisely, video games run on high-performing computers, which have no issues whatsoever in tracking every little piece of trash that the player picks up.
Coming up with (as DM) and tracking (as players) this kind of loot is, however, not viable in RPGs. Additionally, making each of your players roll 15 separate investigation checks for every single ruined house, giving them a broken broom (metaphorically or literally) on a "success" is not fun for anyone. Instead, if they want to loot the ruins, summarize it as
You search the ruins, noticing in the process that they were abandoned centuries ago. Suspecting that you're probably not the first raiders, you attempt to find anything worthwhile left behind. Make an investigation check.
Depending on how roll-loving your group is, you can make everyone roll, or let one person roll with advantage. The latter would mechanically be the Help action, meaning that your most investigative player checks out the place and gets help from the others.
I suggest using the latter version since the first version means that regardless of the DC (unless it's higher than 20, ruling out players with low modifiers), there will likely always be at least one player succeeding on the check. This is less problematic during looting since you can simply scale the loot based on the number of successes, but it will get problematic during boolean checks - i.e., how can I activate this extendable bridge? In that case, only one person has to succeed.
Insisting on the first version would be rather cheesy from your players, but which one you agree on (or which one you choose, since it's ultimately your decision) depends on you and your group.
As a consequence of treating D&D like a video game, your players have unrealistic expectations of you. Make it clear to them that you're not a computer.
The second problem that your group seems to have, which in my experience is not uncommon either, is that they have unrealistic expectations of what the DM can and cannot do.
For example, when your party ventures into a new town, you as the DM can prepare a few NPCs, such as a major, a vendor on the marketplace, and a cleric in a local temple.
Furthermore, when your players suddenly decide to search for a rather exotic kind of NPC, such as an herbalist or a cobbler that you didn't prepare, you should be able to come up with one on the spot, using things like name lists that allow you quickly improve the NPC. (This can be rather hard to do in the beginning, don't get discouraged - it gets easier.)
What you cannot do is to prepare a list of 200 books that a bookstore you potentially just improvised sells. Your players, being accustomed to video games which require years of development (unlike your session), want to look through all of the books to make sure whether or not there's a book that they might like or could use.
You need to make it clear to your players that this kind of preparation would require an enormous amount of preparation that simply exceeds all realistic expectations. This is a key argument, if you can't get your players to accept that there are limits to what you can do and prepare for, it won't work out.
It might help to let other people be the DM in a One-shot, so they realize what they're asking for, but I feel like that would just create other problems down the road (e.g. players trying to tell you that you're doing your job wrong, since they know a little bit about it as well). Hence, I would only choose this means as a last resort.
As a side note, due to the fact that you can't mention every little detail, your players try to jump on every little detail that you do mention. Make it clear to them that, just because you mention something, does not mean it is necessarily relevant to the story or has some hidden meaning. Thanks to @LinearZoetrope for reminding me to clarify this potential issue (which is, btw, the same one I mention in my cow-story at the beginning).
To handle a situation where players want to look through a bunch of books, make it clear that what they want to do is what their characters are doing, but you only present them with the conclusion that their characters came to. Similarly, your players probably don't roleplay going to the toilet (or even mention it), even though your characters most certainly do use the toilet.
You can describe it as following:
Your characters casually walk through the bookstore, letting their eyes wander over the rows of books. Occasionally, one of the books catches one of your characters eyes, but mostly, it turns out irrelevant after all. They ultimately discover 3 promising books: A treatise on the anatomy of Beholders, A complete history of the town of Thunderhall and Dissecting a wyvern: cooking recipes and a guide to poison extraction.
Obviously, you can switch out these books for something more suitable for your campaign. It might also help to have a number of book titles prepared (I'm sure you'll find a bunch on google), so you don't have to come up with them on the spot.
I also recommend you to check out How can I handle players who want to browse shops at random? (disclaimer: I originally asked & answered that question).