LOCAL author Brian John will be present at Haverfordwest Library next Thursday, March 1 (St. David's Day and coincidently World Book Day) for the launch of his latest novel, 'Dark Angel'. 'Dark Angel' is the third book of the Angel Mountain Saga, originally published locally by Greencroft Books and now published nationwide by Corgi.  The novel is (as its name implies) darker in tone than the other novels of the saga, and is a special favourite with female readers. It deals in a very direct way with the terrors and the joys of motherhood.   For this reason, Corgi is promoting the book as a perfect gift for Mother's Day later in the month.    Brian's previous novel, 'Martha Morgan's Little World' (published in a limited signed edition), sold very well before Christmas - almost half the print run has gone already.  This is the companion volume to the whole series of five novels.  The launch at Haverfordwest Library next Thursday at 6 pm, will be followed by a talk on 'Mistress Martha and the Angel Mountain Saga' at 7.30 pm. Light refreshments will be available and admission is free.