I used to call my novel a techno-thriller but most readers stated they wanted to see more action in the very first chapter. At first I thought of complying, but then realized why would I reveal more about my characters or even the plot if I was writing suspense. Suspense is called suspense for a reason, you suspend aspects of the story that are revealed later. How soon does the classification of a work by genre effect readers expectation of events? Not all comedies begin as comedies. And the same can be said about horror or drama. What role does genre selection play in reader expectations?
Suspense is called suspense for a reason, you suspend aspects of the story that are revealed later.
No, that is not why suspense is called suspense. Suspense is a story that is suspenseful in itself. Something bad might happen and the characters don't know if it will or not. They try to prevent it, but they may fail. Some may live, some may die. They don't know, so, in the ordinary unfolding of the story, we don't know either. The author is not holding anything back, they are simply telling a suspenseful story in the order in which it occurs.
Deliberately holding back information from the reader in an attempt to create suspense in a story that is not naturally suspenseful usually fails. It creates annoyance, not suspense. (There are exceptions, but they are crafty exceptions, crafted so that the revelation pleases rather than disappoints. This is no easy thing to do.)
But this does not in any way mean that you have to start with action. If readers are asking for immediate action, that means that they are not engaged with the story, but it is not usually action that actually engages the reader in a story. They are engaged by an interesting setting, and interesting character, as sense that something may happen. The direct dive into action usually does not work because we do not yet care about any of the people the action is happening to.
Genre is a kind of promise to the reader that a story is going to give a certain kind of pleasure. (We should note that there are stories that are set in genre settings or concern genre events which are not part of the genre. Not every novel set west of the Mississippi is a western. Not every novel with a love story is a romance. A genre is a set of conventions that promise a certain quite specific kind of experience for a reader who does not want surprised and does not want to be disappointed. The opening of a genre novel needs to show that the author intends to abide by the conventions of the genre.
Beyond that, though, the job of the opening is the same, regardless of genre. It has to engage. It has to initiate the reader into the place and people of the story in a way that promises that something interesting is going to happen.
I think it depends on the genre and on the readers.
I believe that thrillers and, generaly speaking, tales whose main focus is on action (whatever the genre the book actually falls in) are under greater pressure to kick off with action. Do note, however, that I say pressure, not obligation. Although many readers won't mind a slow start that slowly builds up in tension, it is easy to come across readers who may be considered, if I don't offend anyone, addicted to an adrenaline-filled reading experience and will both expect and demand the first chapter to start in that tone.
I believe that romance may have similar expectations to a different degree in the sense that the book should open with a female character who is obviously 'ready' to meet her true love, one way (e.g. just ended a relationship or longs for one while not believing it may happen) or the other (e.g. believes to be in a good relationship which is shown from the start to be an unhealthy one or which will be abruptly interrupted by tragedy). This one seems to be more of an imposition than the action-packed first chapter, although I'm sure there are successful exceptions around.
I won't buy a book that doesn't clearly signal (on the cover, in the blurb, or within the first page) that it will deliver what I seek. Given the huge amount of books published every week, I no longer give books a chance to maybe turn out to be what I want. I buy those books where I'm sure.
There are different ways to signal the kind of story you are going to tell. One of them is following genre conventions. That's the easiest way.
If you want to "suspend" some information, you must come up with other cues for your readers that won't give away the story but define the story type.
(Your publisher might disclose what you hide in the blurb to attract readers, so your strategy might not work.)