When using the Bodoni Std font that Adobe provided in its old Font Folio 11, Dorico wrongly renders the Italic style (italicized version of the Roman style) like the Book Italic—see the second item in the screenshots.
FWIF, the Book style is mysteriously named Regular in Dorico.
I upload a Dorico file for testing. I don’t know if I can upload these font files publicly here, but I can provide them privately if you want to test this out.
Bodoni Std test.dorico (457.3 KB)
Interestingly, in TextEdit or Apple’s Pages, if I select text in “Bodoni Std Roman” and press Command I to make it Italic, I get the Book Italic.
I suspect the same thing is happening in Dorico, which I think calls the ‘style’ rather than the actual font.
Both the Book Italic and Italic have the same Weight class and Width class, which may make them indistinguishable to some software, and presumably Book (as first alphabetically) wins.
Book is also “Regular” and “Normal”, which may explain why Dorico describes it as “Regular”.
This is the same issue as my favorite font, Iowan Old Style. All my other projects think that my phone is missing… Because dorico keeps looking for regular, rather than Roman.
Regular and Roman should be interchangeable.
However, a quick check through my font menagerie, and I can’t find another typeface that has both Book and Roman/Regular styles: usually if they have a Book, then the other Styles are Medium, Light, Bold, etc.
So, it is something that Dorico should handle more gracefully, but the naming used for that face’s styles is not great.
A definite catastrophe.
Thank you, autocorrect… my “fonts” are missing. 
It is rare, but the original Avenir designs included both. Of course eventually the whole family was redesigned (“Avenir Next”) with friendlier weight designations.
Did you ever find a solution to this problem with Bodoni Std (aside from disabling the book variants)? Still occurring with 5.1.10
