Did the Chinese already use woodblocks to print books in 865 AD?

Yes

Block printing was invented by the working people of the Han nationality in ancient China after long-term practice and research. Since the invention of paper in the Han Dynasty, writing materials have been much lighter and more economical than the oracle bones, bamboo slips, gold, stone, and silk used in the past. However, copying books is still very labor-intensive and far from suitable.

In the Sui Dynasty around 600 AD, people were inspired by engraving seals and invented engraving printing for the first time in human history. Engraving printing involves pasting neatly copied manuscripts on a smooth wooden board of a certain thickness. The front side of the thin and almost transparent manuscript paper is attached to the wooden board, so that the words become reversed and the strokes are clearly legible. The engraver used a carving knife to cut off the non-writing part of the page, resulting in a convex font, which is completely different from the concave font on the stele. When printing, ink is applied to the raised lettering, then paper is placed over it, and the back of the paper is gently wiped so that the writing remains on the paper.

As the earliest printing form that appeared in China. The earliest extant woodblock print is the Diamond Sutra printed in 868 AD (now in the British Museum), but woodblock printing may have appeared about 2,000 years ago. Block printing is known as the "living fossil" in the history of printing. Yangzhou is the birthplace of Chinese block printing and the only city in China that preserves a complete set of ancient block printing techniques. The country attaches great importance to the protection of intangible cultural heritage.

It can be seen that the Chinese had already used woodblock printing to print books in 865 AD