If you aren't familiar with the term, beta readers are people who read your novel or short story before you submit it to a publisher.
Beta readers don't have to be writers. Don't look to them for copy editing (grammar, spelling, punctuation, etc.) although they'll often point out the problems that jumped out at them. I only ask my beta readers about story-level issues. Most of your beta readers are going to come from your circle of writer friends, so build your community.
Beta readers were important to me as I wrote my first few novels but with each novel I use them less. It isn't that I don't want the feedback. My writer friends are busy working on their own novels, editing anthologies, or have real life issues that make it hard to find time to read.
The relationship isn't all about my needs. My writer friends know that I will drop everything to read their work if they need a beta reader. It's community, not a fan club.
I had four beta readers for Night Creatures. Only one was someone I've used before. The other three, well... Two never got back to me so I have no idea if they read it. Telling me you read it but didn't like it is fine. Telling me you got busy is also fine. You're doing me a huge favor. I understand if things don't work out and I really understand that real life has to take precedence. Silence, however, isn't nice. One reader did get back to me, but obviously wanted to rewrite it from erotic horror to erotic romance.I was somewhat relieved when the suggestions to "alpha male"ize my character stopped. Perhaps the part about him not being a nice guy underneath it all (and that being the point) finally sank in. Fourth reader said the ending wasn't dark enough. It wasn't. I lost my nerve and tried to soften it a bit but he said he felt cheated by the tepid ending. That was great input and it gave me the courage to go for the ending I originally intended. (And oh, how I'm laughing at myself for bitching about how Thomas Hardy's books always make me want to slit my wrists because his stories are so bleak, and here I am doing the same thing.)
So, beta readers. They can be helpful, or not. You won't know until you hear what they have to say. Be grateful for their time, but don't feel that you have to take their advice.