The issue is happening because of the nature of QUERYs, in that each column of a QUERY can only return one type of data (e.g., text or numbers, but not both). In the case where multiple data types exist in one column, QUERY will return the most populous type for the column. In your case, you've inserted "-" in place of null, and that is text. I'm guessing that your array formula filled the entire column of empty cells after your data set with that hyphen, making text the most populous type for the column. Therefore, all of your percentages were being converted to text. And in descending order of text, for instance, 9.25% (as a string) is "higher" than 25%, because the former begins with "9" and the latter begins with "2."
One way to resolve the issue would be to remove the "-" from your 'Book Rating'!J2 array formula and replace it with IFERROR(1/0), which will leave those cells null instead of filled with a hyphen. This will leave numbers as the most populous type for the column and your QUERY will work as expected.
Using E13 as an example, here was your original formula:
=Query('Book Rating'!$A$1:$K,"Select A,J where A<>'' Order by J Desc Limit 10")
If you want to leave that hyphen running in the array formula, here are some ways to leave the 'Book Rating'!J2 array formula as I suspect you had it, instead changing your QUERY formula:
1.) Pre-FILTER the 'Book Rating' data before performing the QUERY:
=Query(FILTER('Book Rating'!$A:$K,'Book Rating'!J:J<>"-"),"Select Col1,Col10 Where Col1 <> '' Order by Col10 Desc Limit 10",1)
2.) Use SORTN and FILTER together instead of QUERY, since FILTER can handle multiple data types in the same column:
=ArrayFormula({"Books","6 Stars";SORTN(FILTER({'Book Rating'!A2:A,'Book Rating'!J2:J},ISNUMBER('Book Rating'!J2:J)),10,0,2,0)})
