I don't think it's as cut and dry and race mattering when picking a book. Cultural differences play a part as well. I read a lot of manga, manhwa, and webcomics so a lot of the plot center around Japanese and Korean, respectively, cultural norms. I live in the U.S. so as a reader, I can't help but to compare what I'm reading to my way of life. For others, it may be hard to stay in the mind set of something so different.
I will say that I'll be more inclined to pick up a story if I know the characters and/or the authors are black. I'm black and it honestly feels good to see that representation. Will I pass up a story because the characters are white? No, however, typically in literature, white is usually the default so when I read a book I assume the characters are white until described otherwise. I know I can't identify with them on that front so I look to other things like their age, personality, occupation, etc.
Your novel for example. I'll assume Jamie isn't black. While I can't identify with her there, I can tell she's super enthralled in her work constantly wants to gain knowledge. She's also good with fixing things and has a bit of a curious streak, Those are things that I and others can identify with.
And as writers we can't help but do self inserts and model our characters after ourselves in some way. This isn't inherently wrong either. It also goes beyond race, representation on any front is important and allows people to feel seen and know their respective experiences matter.
I didn't mean for this to be so long sorry