I read many novels which go into a lot of detail about what characters looks like. Some even go so far as to tell me what they are wearing and usually it does nothing to move the story on. If a person is dressed inappropriately or extravagantly that will tell me a bit about their character, but describing the softness of the shoulder pads in their shirt and the ripple of their stone-wash jeans when they are sitting around home just mires the story in a time period. Fine if you want us to be in the 80s, but a lot of stories could easily go across times if the fashion didn’t get in the way.
Then you get stories at the other extreme (which probably most of mine fall into) where you are lucky to get a name for the character. I’ve actually done it once where I was writing a first person story and didn’t even drop my character’s name into it. This can be done successfully (mine wasn’t), but I think there are two important things that you (usually) need to specify about your character; gender and approximate age. All the rest can be up to the reader.
The book I’m reading at the moment did not mention the main protagonist’s age, so for some reason I got it into my head he was a middle-aged man. It was only at the half-way point in the book that I was told he was in his early 20s. That went some way to explaining the excessive running and apparently inappropriate relationships with a (I thought) much younger woman. I wish the author had mentioned it earlier. The character underwent a painful morph into a younger self in my head, but he keeps slipping back to his portly, balding older self as I get back into the story.
Of course different readers want different levels of description, so all I can recommend is write what you like. I often get told off for not showing my readers what colour my character’s hair is, how tall they are etc. The way I see it is if it is important to the story, or if I’m going to mention it again later, then I’ll tell you when you first meet. Otherwise, make the character your own. Every book is experienced by each reader differently and that is part of what I love about books over movies.