Like a few other reviewers, we arrived during normal opening hours to find the shop/admission office closed. However, the gate was open (and being existing Historic Scotland members :-) ), we went through the open gate.
Some excellent restoration just outside the chapter house and excellently tended grounds.
Very nice place.
As a tourist attraction, the absence of staff portrayed a very unprofessional image and, if any of the Historic Scotland sites needed their normally excellent guide books, this is one of them. Pity there was no one around to sell it.

Glenluce Abbey is one of the least complete abbeys in the area (Dundrennan, Sweetheart), but it is still interesting. The best thing about our visit was the flowers growing in profusion on the ruins. Even though we visited during Historic Scotland posted hours, there was nobody in the office or on the grounds to answer questions.

Drove along the scenic coast to Glenluce; arrived at the abbey only to find it closed in winter. Tbh I'm not sure I'd have paid the £4.50 entrance fee anyway as it's only a small abbey and not sure it would've taken long to walk round. We got a couple of pictures from the car park anyhow and it is pretty :)