Linshu 麟書 "Book of the unicorn" is a "brush-notes"-style book (biji 筆記) written during the late Northern Song period 北宋 (960-1126) by Wang Ruohai 汪若海 (1101-1161), courtesy name Dongsou 東叟 (Dongsou 東叟 might also have been his style).
Wang hailed from Shezhou 歙州 (modern Shexian 歙縣, Anhui) and became a student of the National University (taixue 太學) in 1126. During the first attacks of the Jurchens on the Song empire he submitted a memorial to the throne. In his letter to Councellor Cao Fu 曹輔 (1069-1127) and Wanyan Zonghan 完颜宗翰 (also called Nianhan 粘罕, 1080-1137) he suggested to make Zhao Gou 趙構 (1107-1187, the eventual Emperor Gaozong 宋高宗, r. 1127-1162), Prince Kang 康王, Grand Marshal (da yuanshuai 大元帥). Yet the capital Kaifeng 開封 (modern Kaifeng, Henan) fell into the hand of the Jin empire 金 (1115-1234) of the Jurchens. When Zhao Gou founded the Southern Song 南宋 (1127-1279), Wang Ruohai was made fiscal commissioner (jingzhishi 經制使) of Jiangan 江南 and then supervisor of the public petitioners review office (jian dengwen jianyuan 監登聞檢院). In 1139, he was appointed gentleman for discussion (chengyilang 承議郎) and then rose to the position of controller-general (tongpan 通判) of Shunchang 順昌, and finally to that of prefect (zhizhou 知州) of Jiangzhou 江州.
Wang Ruohai's thoughts about the disintegration of the Northern Song court and his suggestions for its eventual rescue are reflected in his book Linshu that is written in a very elegant and refined language. The "unicorn" (lin 麟) is the symbol of prosperity and an auspicious omen of a prospering government. With the parable of the unicorn Wang wanted to urge the Song government to display more military resistance against the Jurchens instead of negotiating peace. He moreover criticized the dismissal of Prince Kang from the post of highest commander and explained that Emperor Qinzong 宋欽宗 (r. 1125-1126) would have to defend the altars of soil and grain (sheji 社稷), symbol of the dynasty, with his own life. Many thoughts in the Linshu are not expressed directly, but in allegories, because the capital had already fallen into the hands of the enemy. At the end of the short book, three postfaces are attached, written by Deng Su 鄧肅 (1091-1132), Lü Benzhong 呂本中 (1084-1145), and Wang Ruohai's uncle Wang Zao 汪藻 (1079-1154).
During the Ming period 明 (1368-1644), the Linshu was included in Wang's collected writings Wang Ruohai ji 汪若海集. It is also to be found in the series Xu baichuan xuehai 續百川學海, Baoyantang miji 寶顏堂秘笈, Manggue jieshu qianji 蘉古介書前集 and Shuofu 說郛.