Yes, a sketchbook is a beautiful thing and I don't just mean "aesthetically". As a matter of fact, I don't mean "aesthetically" at all! You've probably seen fantastic, inhumanly good sketchbook pages on blogs out there. You can search the phrase "my sketchbook" and you'll find drawings that make you want to give up altogether because they are so fantastic, but please, if you take my advice about anything at all, please don't be intimidated by anyone.
I used to feel put upon to make every page in a sketchbook interesting and "artistic" in case someone looked inside my sketchbook and saw some wonky-looking drawings. Now I keep sketchbooks going for myself, they are just notepads filled with "notes" to myself. Mine have many, hideous, awful drawings where the eyes aren't even or the ears on a person are too low or (this is a big problem with my sketches) I don't give my faces nostrils! So the people I made on paper are going to suffocate!
Keep a book going, it's awfully entertaining. You'll find that you like waiting in line because you can play in your little sketchbook. You can practice drawing people in the grocery store, in church, at the school board meetings (it definitely makes those more tolerable). I made a deposit at our bank one day and the teller smiled and showed me the picture I had drawn on the deposit slip without thinking. Now she asks me if I have any new sketches to show her when I go there.
Your sketchbook can be anything. It can be something you bought at the art store that says "Sketchbook" on it or a single subject spiral notebook from Walmart. When I was in college I was so broke (how broke were you?) I was so broke that I made my own sketchbooks out of computer paper. I took an old book apart and used it as a pattern to make sketchbooks... they were hideous! I was surprized lately when one of my sons found one of the old books and told me how much they meant to him sentimentally and how cool he thought they were.
Get something you are not afraid to mess up and mess it up! Then get another, and another. You'll improve, you really will! I need to mess up many more too. I remember when I had 1 or 2 sketchbooks and I could never imagine filling them up.