I have been wanting to do karate since I was a kid, but never was able to and now I am going to start Shotokan and I want to know is it a good martial art to learn?
It is excellent for protection.
tedhyu gave a great answer, you must be committed to any martial art, shotokan is no different.
And you have to have a good instructor. If you have that combination of a good teacher, and total commitment, you will do very well.
Like anything else, Shotokan is only good if you are committed to it. I started when I was 29, and I know people who started much later. Commit to the art. Accept the corrections from your seniors. Get low on your stances.
It's ok, very good for kids especially as its simple and direct in its movements.
Shotokan Karate is actually from Shaolin kung fu styles. A japanese spy during the war ended up training in the Shaolin temple, then came back to Japan and basically butchered kung fu and karate into one. They have very different principles though, and you mighty have issues absorbing it as a complete art.
Shotokan is preferable to normal Karate, but kung fu (NOT wushu) is more preferable to that.