Chuang, the great anti-CPC communist group in China, by far the greatest providers of class struggle analysis and reporting from there, give us this gem on the topic of this book:
"Prototypical of this problem is the example of the Shanghai Textbook. Originally published as the Fundamentals of Political Economy in Shanghai in 1974, during the peak of state influence during the “long” Cultural Revolution, the book was meant as a summary of Party ideology at the time. Ostensibly describing “socialist political economy” as theorized and practiced in China, the textbook was translated and published, with accompanying essays, by American Maoists under the name Maoist Economics and the Revolutionary Road to Socialism: The Shanghai Textbook. The textbook, alongside other collections of state propaganda and reports from foreigners’ tours of model factories, has been taken as a common reference point for both supporters and detractors.
The problem, for either political persuasion, is that the data laid out in the Textbook is purely mythological. The text’s theoretical poverty aside, no system such as that described by the book ever existed. By the same token, the practices observed by touring model factories were often limited to those factories. Though some features were obliquely shared between reality and these Potemkin villages, all the fundamental characteristics were different. The Textbook is better understood as a sort of religious text rather than a description of the socialist era’s economy. Tours of model enterprises became a kind of pilgrimage, reinforcing the holy status of such texts for Western radicals. Scholars basing their studies on policy pronouncements are then engaged in a sort of glyphomancy, pulling apart the minute details of leaders’ speeches and rearranging them to fit whatever narrative one wants to tell."
Perhaps because they're heavily involved in Chinese leftist politics and not US ones, they don't specify that said American Maoists were the RCP, an infamous personality cult around its chairman, Bob Avakian, with a truly embarrassing history.
As for the book itself, it is digitally available and if you want, with a critical mind, look at the most blatant Stalinist propaganda to fool the fools that want to be fooled, here you go. If you want actual Marxist critique of political economy, however, this is just about the most hilariously blatant and extreme falsification of Marx and Lenin possible.