It is perhaps a minor mark of my descent and status that I have spent a certain amount of time wandering around parklands attached to stately homes, or about botanical gardens. There is a certain odd feel to this; something a little unsettling about bright sunshine and places built to take advantage of that. It is not an environment untouched by human hands, or one shaped for a specific function, like a ploughed field (which still retains certain characteristics of landscape and place). Such gardens are larger than any mansion: they are not enclosed by a ceiling; even a greenhouse is in some sense open to the sky. If such a place is well-kept and tended, it takes on a feel of its own, quite unlike other sub-urban gardens, carefully kept in line with their homesteads, or the minor cultivation of a village green.
The process of walking through them, as an outsider, need not be off-putting (though the carefully planned village and grounds of Portmeirion was used as the set for that classic of television The Prisoner for a reason). But it is quite different from many other such interactions. A few things come close: exploring some of the sites of Classical Greece and Rome - my mind goes more towards Olympia and Epidaurus than Pompeii or Mycenae (bits of the video game The Talos Principle get close to this) I think a long time spent in the rows of a vineyard might come close. A garden centre or nursery might also be like this, in a distant and diminished way (the commercial aspect is distracting - archeological sites and stately homes only try and sell you something in the gift shop).
All this may well be by way of saying that Emmy Allen is mining a promising seam, if she wishes the Gardens of Ynn to truly be, as the subtitle has it, gardens 'of surreal delights'. What is more, I suspect that the garden element resonates a little stronger in this work than any element of the inspirations she cites - however clear the signs of Wonderland, Narnia or Ghibli are in the paths of this enchanted place.
I shall note, by way of ending this segment, that Gene Wolfe knew what he was doing in putting temporal distortions and unrealities in the Botanic Gardens in the city of Nessus (The Book of the New Sun, The Shadow of the Torturer) - and also that if you plan to run The Gardens of Ynn, it would be worth spending a few hours in a set of gardens yourself, acquiring the grammar of horticulture before attempting dialectic or rhetoric (consider also this interview with Jacob Hurst; spend some time with a flower catalogue or some other source of botanical vocabulary).
Of the Gardens of Ynn, then, what may be said? They are a set of gardens, in a 'perpendicular world', accessed by supernatural -if worryingly simple - means. But this once luxurious place has been devastated: it is in ruins, with the machinery that once sustained it erratic or broken. The creators are dead, fled or debased. That which destroys it lingers still - as do many of the inhabitants. [More aesthetics of ruin?]
The environment it invokes is both marvellous and pitiful: think of an abandoned or neglected greenhouse, the plants within grown too large, pushing dusty panes of glass out of shabby frames. I have emphasised above the strangeness of a well-maintained and vast garden (vast in terms of size, but sub-divided many times into discreet areas: walled gardens, hothouses, firing ranges, hedge mazes - few, if any, rolling fields). Allen provides a decent collection of ways in which it may be very much not well-maintained. My instinct would be to allow the early stages of exploration to be in relatively well-preserved and uninhabited parts of the Gardens. The exploration system leans towards this, though it would not ensure it. Perhaps Layer Zero (that closest to the point of ingress) could have a few sub-divisions explorers wander through as a kind of overture to set the mood of the piece, though it would be likely contrary to the feel of Gardens or OSR principles of design to have this continue for long.
Those ruined locations are naturally teeming with danger. Ancient devices and magics abound - often of a genteel, tough hardly less than perilous disposition. The location details table offers a double layer of variation to all this (and could again be left of for Layer Zero). The parasite table is, naturally enough, teeming with all the horror things that grow or crawl can produce.
On top of these, the beasts and inhabitants that still roam the gardens have the same air of distorted purposes and reduced natures: golem gardeners or those decorative raptors, the peahawks. Here especially Allen shows her influences in the form of living chess sets and piscine or batrachian servants (and, yes, The Jabberwock). The presence of vast Ambulatory Puddings is inexplicable (does one make or consume puddings in the garden?) but very welcome indeed. There are twenty puddings and they are all super; I may have to make a few of my own.
All this is without considering the dreams, or mysterious musics that provide insight through 'synesthetic psychedelia'. Likewise, without considering that which devastated the Gardens, or what those Gardens become in their furthest extremities. I shall not venture to say much on either. Both are in keeping with the air of the Gardens, but there is no perfect end or final act to The Gardens of Ynn. This is quite proper: it is an interlude, a stroll in the gardens - not a forced march, an epic trek or a cavalry charge. This might be smaller, but it is not lesser, or shabbier. Besides, you are warned going in that it is for lower-level (if not lowest level) parties.
Give it a try, by all means. But it may be something that needs easing into: a tone must be evoked and set by a conscientious GM - just like any other adventure, perhaps. But certainly the case in this tight and enclosed place of magic and artifice.
See here for Emmy Allen's blog and here for a place to purchase The Gardens of Ynn.