The Mysteries of Udolpho

An excerpt of a review from The Monthly Review [published in 1794]:
IF the merit of fictitious narratives may be estimated by their power of pleasing, Mrs. Radcliffe's romances will be entitled to rank highly in the scale of literary excellence.
The works of this ingenious writer not only possess, in common with many other productions of the fame class, the agreeable qualities of correctness of sentiment and elegance of style, but are also distinguished by a rich vein of invention, which supplies an endless variety of incidents to fill the imagination of the reader; by an admirable ingenuity of contrivance to awaken his curiosity, and to bind him in the chains of suspense; and by a vigour of conception and a delicacy of feeling which are capable of producing the strongest sympathetic emotions, whether of pity or terror. Both these passions are excited in the present romance; and we admire the enchanting power with which the author at her pleasure seizes and detains them. We are no less pleased with the proofs of found judgment, which appear in the selection of proper circumstances to produce a distinct and full exhibition, before the reader's fancy, both of persons and events; and, still more, in the care which has been taken to preserve his mind in one uniform tone of sentiment, by presenting to it a long continued train of scenes and incidents, which harmonize with each other.
Through the whole of the first volume, the emotions which the writer intends to excite are entirely of the tender kind. Emily, the heroine of the tale, early becomes familiar with sorrow, through the death of her parents; yet not before the reader is made acquainted with their characters and manners, and has accompanied them through a number of interesting circumstances, sufficient to dispose him to the exercise of tender sympathy. At the same time, her heart receives, by slow and imperceptible degrees, the soft impressions of love; and the reader is permitted, without the introduction of any dissonant feelings, to enjoy the luxury of observing the rise and progress of this passion, and of sympathising with the lovers in every diversity of sentiment, which an uncommon vicissitude of events could produce; till, at last, Emily is separated from her Valancourt, to experience a sad variety of woe.... We should have great pleasure, would our limits permit, in giving to our readers some specimens of these descriptions.
Something of the marvellous is introduced in the first volume, sufficient to throw an interesting air of mystery over the story; and the reader feels the pleasing agitation of uncertainty concerning several circumstances, of which the writer has had the address not to give a glance of explanation till toward the close of the work, in the remaining volumes, however, her genius is employed to raise up forms which chill the soul with horror; and tales are told that are no less fitted to "quell each trembling heart with grateful terror," than those with which, "by night,
"The village matron round the blazing hearth
Suspends her infant audience."
Without introducing into her narrative anything really supernatural, Mrs. Radcliffe has contrived to produce as powerful an effect as if the invisible world had been obedient to her magic spell; and the reader experiences in perfection the strange luxury of artificial terror, without being obliged for a moment to hoodwink his reason, or to yield to the weakness of superstitious credulity. We shall not forestall his pleasure by detailing the particulars: but we will not hesitate to say, in general, that, within the limits of nature and probability, a story so well contrived to hold curiosity in pleasing suspense, and at the same time to agitate the soul with strong emotions of sympathetic terror, has seldom been produced.