This font was used in a book published as a first edition in 2013 from what I was told.

I looked for it using a number of automated tools, but there are not enough characters for they to work.

Any ideas of what it could be? I suspect the font is not so common, but typography is not my strongest point.

Art Gothic URW is close, but the lowercase c is different.

Pretty sure you already identified the source: Art Gothic. But it was once a metal font and the digital versions all look a bit differently. 

Commercial:

• Art Gothic URW
• Dexterous
• Art Gothic Hi H

There are also free versions floating around on the internet if you google “Art Gothic font”. The c should be a better match with these version. Not sure if they are legitimate. 

P.S. The style is called Art Nouveau—nothing Celtic about it. 

 

Thank you, Mr. Herrmann.

I edited the post title to better suit your reply.