Perhaps, though, other equivalent phrases can highlight the difference in usage if you replace except for with with the exception of and other than with apart from then we have are there any. The string an other is vanishingly rare in english. In contrast another is positively pervasive.

There's a formula: Another = an + other. Think of it as of an article plus the word other that have historically merged into one word. Grammar requires some article before other book; Either the or.

Either the or.