Wicked question

I read a book probably about a year ago. I thought it was titled spellbound, or maybe it was the first book in this author's "Spellbound" series. It was loosely based around the wizard of oz, but it is completely different. It's not Wicked, but the cover featured a black background and ruby slippers shining with like a green smoke around them I believe.

I know in this novel there were dragons, a dragon cave, a rainbow of some kind which like ha some sort of significance. I think Toto might have been like half dragon. I don't even know, and it's killing me because I want to read it again and read the sequel which I do remember came out in 2016.

I know all of this is so vague, but if you can help me, I'll really appreciate it!