Nocturne in E major

I have composed a few nocturnes. This is my first one. It is very simple. Any advice for how to improve is of course appreciated.

I think it's an excellent example of romantic nocturno.

There's a total lack of expression slurs, which I suppose are played.

The harmonic change from measure 22 to 23 is a bit abrupt, but the changes that come afterwards are very nice.

Although sometimes you break the left hand pattern, it's just for a moment. I think some contrast in that hand is always welcome. The arpeggios and broken chords are very beautiful, sometimes chromatic; but some contrast reinforces the second coming of the main theme.

The end is a bit long because the chords don't bring anything new.

Anyway, these are suggestions. I think your piece is quite nice.

m. 5, Bb should probably be A#, as it's a lead to the dominant as the next note of the melody.
In the beginning the parallel octaves in between both hands is harmonically dry.
m. 20 - no reason for the left hand part to be so empty. I get the effect you're going for, but the register of the left hand prevents it.
I agree with Luis about the ending being long for the same reasons. Feels like an A' section and not an ending per se.
I was mostly a fan of all your chord progressions. 
The rhythm of the melody didn't have to be so standard, I feel. It's a bit to beat-magnetized... like it overemphasizes the beat, which is okay in some situations, but this functions less like a waltz and more like flowing ambiguity, which your melodic rhythm prevents occasionally. 

That is very helpful feedback. It is good to get such useful advice. Thank you both, I will apply this advice to the piece.

Okay, I have tried to update this piece based on the advice given. Please do let me know if this is a step in the right/wrong direction. Your feedback was very constructive, so thanks for that.