The 2018 HOn3 Annual from White River Productions has now made it to UK stockists (I don’t think it’s been out that long in the States either). I’ve just ordered mine from Bill Hudson Transport Books. From the list of contents, it looks as if there’s a particular emphasis on the East Tennessee & Western North Carolina this year:
http://hon3annual.com/current-issue/
HOn3 Annual 2018
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All narrow gauge other than On30 etc
Contact: Nick Prior
All narrow gauge other than On30 etc
Contact: Nick Prior
Re: HOn3 Annual 2018
Funnily enough, the HOn3 Annual 2018 is also available from fellow NMRA members Linda Tinker Railway Books 
Just one title of the 2,000 North American Railroad books we have at the moment. See our full page ad in ROUNDHOUSE every issue.
Linda & Rob
Just one title of the 2,000 North American Railroad books we have at the moment. See our full page ad in ROUNDHOUSE every issue. Linda & Rob