How to not lose your friends before you make them.
Okay, so I am by no means an expert on writing. Honestly, I'm not sure anyone ever really is or can be because it's such a subjective thing, but there are skills associated with writing that can be generalized. One of those skills is the handling of backstory.
Backstory can turn into a serious thorn in the side of any author. There's so much to the characters that we want the readers to know and enjoy that it's tempting to put it all in the story from the first paragraph. We can delude ourselves into believing it's needed information and indulge our "creativity" by letting the backstory choke the "real" story.
When writing a story, think of it like making an introduction to someone you've never met - that is, after all, what you're doing. You're introducing readers to the world you've created. Imagine sitting down at a table to introduce yourself and, rather than just converse, the person you've just met starts rattling off their ENTIRE LIFE STORY without preamble or reason. It doesn't matter that this information is the basis of what made this person who they are; you don't need or want to hear it. Beyond that, it's just weird and rude to talk about yourself like that.
Yet, so many times, that's what (especially new) writers want to do with their characters.
Readers don't need a front-loaded version of the character's history any more than a new acquaintance needs the Cliff Notes Guide to You. If you treat a readership like a friendship, and share the information when it's appropriate, then everything will come out when it needs to. There will be mystery and intrigue, and the kind of secrets and kept back information that make a person unique (and tolerable) to those around them. Readers will seek to discover more, rather than force themselves to trudge on.
People can read books written either way, but most will choose to revisit the ones that don't force feed them information like a boisterous guest who doesn't know when it's time to leave the party. Just like people are more apt to visit friends than annoyances.