I also enjoy reading old computer manuals. You can learn a lot from reading them about how to structure technical material and how to write clear explanations (without assuming the reader is an expert). Sometimes, it's even a pleasure to read old computer manuals. And who can say the same about documentation today?

Here are two excellent examples of computer-related writing:

Usborne 1980s Computer Books

These books have been discussed a few times before here on Hacker News. Children's publisher Usborne have made available for free some classic computer books from the 1980s aimed at kids. The books use illustrations extensively to explain concepts. Not only are these books well written with clear, concise explanations, they are also more readable and enjoyable than many programming and computing books published for adults today. Anyone writing a technical guide (of any kind) would benefit from reading these as a source of ideas and inspiration:

https://usborne.com/gb/books/computer-and-coding-books

Visual Basic 3.0 Language Reference manual (1993)

Every entry in the Language Reference manual is formatted in a clear structured form. It still stands as an excellent template for any programming language reference:

Property name

- Applies to

- Description

- Usage

- Remarks

- Data type

- See also

- Example

Scanned PDF (16mb): http://win16.info/files/vb/3/Reference.pdf