This is a terrific exhibition and really worth going to see. Take your brain and a willingness to explore. And if you read Mandarin you'll have the advantage of me, but the great point of Xu Bing's work is that it transcends and challenges language: there is delight in the detail here for everyone, whether or not you know anything about Chinese script or traditional Chinese or traditional Western painting. Paradoxically, this is true even though the work is largely based on just those things: Chinese and Western artistic traditions and calligraphy. You can't imagine the scope this provides until you have stood in front of some of these pieces and absorbed the extraordinary detail.
The best thing to do first is to go straight to the four tall pieces (77a-d;The Suzhou Landscripts) dominating the far wall of the middle room. These pieces are at the heart of the exhibition. Like everything else in the show they are monochrome, and like most things here they depict, lovingly and with skill, beautiful landscapes. They are in fact copies - copying, or rather versioning, is an honourable mode of creativity in traditional Chinese art - of four classical Chinese landscape paintings. But in these four paintings, the artist has traced over the top in red the shapes of the Chinese characters which, one discovers, have actually been used to form the brushstrokes of the relevant part of the picture. The water is composed of the word for water; the mountains are composed of the word for mountain, over and over again.
Other paintings show crops, doors and windows, boats and animals, all composed of their Mandarin characters. It is as though a western artist (Magritte perhaps) had painted a tree in which all the leaves were formed of the word "leaf". With the crucial difference that Chinese calligraphy is built for this purpose: the words are in fact formed of pictures of the concepts in the first place. This lends the letters a flexibility and grace that means that even if you don't know Mandarin, you are captivated by the expressiveness and life of the picture formed by the shapes of the writing.
Xu Bing's fascination with language has even led him to write a four-volume book in an invented 4000-character language reminiscent of Chinese calligraphy (the Book from the Sky, 1987-91). He has been engaged since 2003 on a complementary, not to say opposite, project: a new pictogram writing system intended to be intelligible to anyone regardless of language.
Many of the pictures in this exhibition have what appear to be Chinese characters captioning them in the classical style. But look closely. They are actually English letters bent and melted into the shape of Chinese pictograms: each pictogram is an English word. This Square Word Calligraphy is a perfect medium for Xu Bing's concerns with the barriers and bridges between languages. It dances provokingly along the line between easy and maddeningly hard to decipher, and all through the exhibition you will see people standing glaring fixedly at it, muttering to themselves in puzzlement or triumphant recognition.
There are three rooms, broadly tracing three stages in the artist's development. The first room contains early pieces in the Western style, which was the practice for artists in China during his studenthood, following the Soviet model. There are some beautiful things here. To a western eye these pieces are saturated with feeling: the landscapes hold impressions of loneliness and distance; the interiors are inviting and jolly with pots and pans. Some were drawn on wrapping paper with children's crayons - the only materials available to him at times during his "re-education" in the Cultural Revolution. There are fine studies of Western masters: sketches by Millet and Pissarro are laid side by side with them to show exactly where that style was coming from.
There's a definite transition in the 1970s, when China was opened up and Xu Bing was exposed to pop art for the first time. The style changes radically: you can see where a realistic sketch of a hill full of fields in the sketchbook has been morphed, stretched and squished into several finished pieces which are much closer to a Hockney-like abstract.
The second room is dedicated to "landscript", like the Suzhou paintings, and it is captivating. If you are interested in Australian Aboriginal art you will find a lot to intrigue you here, specially since China is now considered our best guess for the origin of the native Australians. The use of pictograms as brushwork has distinct parallels with the landscape-focused map-stories of traditional Australian paintings. And it is fascinating to see how thousands of years of separate development can lead to two artistic cultures which are so very different, so elaborate and so powerful.
The third room is possibly my favourite, containing as it does The Forest Project, the result of Xu Bing's involvement in a 2005 enterprise set up by conservation organisation Rare. 
The Forest Project - click the image to open a larger version in a new window © Xu Bing Studio
Xu Bing asked children to draw trees - some of the childrens' pictures are displayed here - and then took their drawings and copied them into huge pictures of forest collectives. They have a wonderful Quentin Blake-like style, which must be derived from the intent re-versioning of children's work by a skilled adult hand. The children's paintings are then auctioned to make money for re-forestation projects worldwide.
This third room also contains The Mustard Seed Garden Landscape Scroll. The Mustard Seed Garden Manual of Painting is a comprehensive seventeenth century manual detailing all the brush strokes you need to master in order to be able to paint in Chinese. Here are all the brushstrokes which form the words/pictures for trees, mountains, rocks and so on. It is, as Xu Bing states, a dictionary. His scroll of images taken from the manual, displayed next to the relevant original pages, give you a chance to appreciate the stunning precision of his work as a copyist. Mountains from the Mustard Seed guide turn up on the scroll as exact copies, perhaps with a couple of figures switched round and a few birds thrown in from a distant page.
It's a massive and thought-provoking exhibition and you'll want to allow an hour for it at the very least. It's the Ashmolean's first major exhibition of contemporary art, and they have commissioned a special mobile site to go with it containing audio clips, video and extra information to complement the exhibition. You can access it via the plentiful QR codes using the gallery's free wifi, or visit http://www.meetxubing.com/en to find out more. But the real beauty of the pieces has to be experienced in person: a bargain, I think, at £6.