I often learn by reading, and I have computer science as my background. I never learn music for 23 years. Is it possible for someone who never learnt music at all at this age to learn music? I want to learn to play piano. Kind of music I want to learn is like covering a song into a piano only song (dunno what is the name), I want to learn cover song like anime song, or normal pop song. So where do I start? Can I do this autodidact? I'm willing to read a thick book :)
Yes, it's possible. However, real-time skills like playing an instrument or piloting a radio-controlled aircraft differ from skills like writing a software package or a book manuscript. What a human real-time observer of your activity (a "teacher" or a "buddy") gives you is personalized shortcuts to improving your skill, orders of magnitude faster than a reference library or a search engine. Try this song next, careful with the rhythm here, that second verse sounded too mechanical, that sort of feedback.
If you compare playing an instrument to playing a modern videogame, then a teacher is like a walkthrough -- but for a game that changes and adapts to you every week as you try different techniques and discover different songs, a game whose outcome is different for each person, a game that remains rewarding even after ten thousand hours of play. A pre-written guide is only a pale shadow of such help.
Contrariwise, the real work of learning an instrument is at home, not once a week in a lesson. Insofar as that is true, all performers are autodidacts.
You know that the answer will be "Yes" right :))
In your age, it's a bit harder if you want to learn music from the beginning, it would be easier if you have some friends help you work with it. If you're autodidact, you must find a good resource (books, play-along, tracks, more).
If you want to start playing pop, anime songs, perhaps you should play some easy children song that you like (a bit nostalgia maybe?). You can find those easily in the internet.
While learning some easy songs, try to learn chords and scales.
I think thats enough. Oh, don't forget to search for motivations :D
I have a computer science background, too. Let me start by saying that you can read documentation on code and grind through just about anything, but music is a different creature (for me anyway).
Know that everyone learns music differently. Some people do great with sheet music, but why don't you try learning to play by ear? I first learned by forcing myself to learn a song I really liked by watching videos and synthtopia recordings. I learned what chords go with what and when the transitions occur. Then, I tried to play along with songs, fine-tuning rhythm and further learning when to change chords. Then, I found some friends to jam with. It was the best thing to ever happen to my music skills - hands down.
I'm not saying it's for everyone, but I've helped several people from my area to learn to play music. In my humble opinion, most of those people play better than anyone I know that plays strictly from sheet music. It's not because I taught them, but because they taught themselves and love music.
These are all good answers. I would consider all the advice given here equally: reading is important, theory is important, playing by ear is important, practice is important. Keep in mind that the process that you used to learn software development is very similar to that which you will use to learn music. You didn't learn to write software entirely from a book; at some point your native creativity took over and allowed you to apply the book knowledge in real-world situations. Same with music.
Also keep in mind that there's strong evidence of a correlation between musical talent and software coding talent. If you want to create music, you may very well have the talent for it.