difference between asu and ashita

Hi, I have a question for you guys,

When do we say あす and when do we say あした ?

And one more small question. Is there a difference or can I say both:
Yomu koto ga suki
and
Yomu no wa suki


Thank you

1) It's an issue of formality. In formal situations, use あす (or みょうにち, even). More casual everyday type conversations utilize あした.

2) You can say both, and there's a difference. I'll leave aside the wa/ga issue that you (unwittingly?) brought up, and say that no is used more for more emotional type words like suki and kirai because it has a more emotional feel to it than koto. Koto is used more for things that are colder and more logical sounding. The reason that I've read for this is that the voiced nasal sound of "n" is warmer and more emotional than the colder, harder voiceless sound of "k."

Ok, well i will hit upon the は、が part. If you say 読むのは好き、instead of 読むのがすき, it implies that there may be some other things which you do not particularly like or have an opinion about compared to reading, within the surrounding the context of your conversation. If you say 読むのがすき though, it simple just means you like reading.

and Glenn is right. の is more personal/emotional, whereas こと seems more distant/logical to the speaker. for example... it is better to say 税金をあげることが必要です。 It is necessary to pay taxes. The reason こと is better is because paying taxes is more of a social obligation, and really nothing personal to the speaker.

Very good explanations as usual, thank you so much