Source: I spent 7 years working at one of the major publishing houses.
In a nutshell, it is extremely unlikely that a publishing house will pick up your book without it being submitted through a literary agent. You can always self-publish, but that of course comes with no support or marketing/publicity, so if you're really looking to have a successful book, a major house is the way to go. (Penguin/Random House, Harper Collins, etc) I'd look at comparable books on the market that are written in a way that you like and respect - the agent will almost always be thanked in the credits. Then you can start the query process of reaching out to those agencies - there are plenty of websites that will teach you how to write an effective query letter.
Good luck!