Who should read my book?
Question After I finish my book should I have some of my friends and family read it before I send it to an agent or publisher so I know if it's good or not? 0r should I just send it to an agent or publisher? or does it not really matter?
Before you send a query letter to an agent or publisher, you want to know your manuscript is the best it can be, because that will improve your chances of making a sale.
Sometimes, we are so close to our work that we don't recognize if something isn't working. With that in mind, it can help to get some feedback from other people who approach it from a different perspective.
Bear in mind, you have to take feedback differently according to who is giving it. Family and friends might be overly kind in some ways. On the other hand, they may not be the ideal audience for your story. And they may not have a lot of expertise in writing.
If they generally like books in your genre and can be honest, they can be a good source of feedback. However, what you want to pay attention to is not what they say about the book as much as how emotionally engaged with the book they become. More engagement is better.
If they don't show much enthusiasm or emotional response, that can be a bad sign. But you must use your judgement. Sometimes people you know can
be jealous or surprised by what you write and that can make them less appear less responsive (for instance, you write a steamy sex scene that turns them on, but they don't want to admit it and they can't believe such graphic thoughts came out of your innocent head because they always thought they were more worldly than you).
Also, average readers can usually tell you what they liked about the book, or what parts bored them. But they aren't often good at telling you how to fix problems (even if they think they are). You have to figure out how to improve the story on your own.
An alternative is to show your book to people who have more expertise, such as other writers you know. Sometimes you can get free inexpensive critiques from pros, but you have to hunt around. Conferences, for example, often offer such opportunities. (You can also pay a lot of money for critiques, so be careful.)
A lot of writers find it beneficial to join a writers' critique group where everyone critiques each other's work. Even then, you have to use your own judgment regarding the feedback you get. Some groups are better than others.
At the very least, it can be quite helpful to have a friend who is good at grammar and punctuation proofread your work before you submit it. A fresh set of eyes can often spot simple errors that you don't (because we tend to gloss over our own work).