Custom post type and URL

Is it possible to remove alias from custom post type? Let me tell a bit more. For instance, I’ve created a post type, name “Book”. So URL will be domain.com/book/post-title or domain.com/?post_type=book&p=528. I want the URL as domain.com/post-title.

Is it possible?

In short – you cannot, or at least should not.

www.domain.com/post-title is interpreted as post (if your structure is %postname%) and/or a page – and WordPress is set to deal with them as such, including any conflicts.

You can do the following:

add_action('init','wpse0845_add_rule');
function wpse0845_add_rule(){
    add_rewrite_rule("([^/]+)/?",'index.php?book=$matches[1]','top');
}

(and then flush rewrite rules, once).

However, you’ll notice that now your pages (and depending on your structure, posts too) give a 404.