Books about the Windows operating system are assuming that the user has never seen a computer before and needs guidance for most tasks. The typical windows book explains, that a computer consists of a mouse, a USB interface, a printer and a monitor and the user is asked to start a program or modify settings in the menu.
It doesn't make sense to transfer this language style to Linux operating systems because Linux wasn't created for computer newbies but for experts. The simple difference between both user groups is, that computer newbies can't program in Python while computer experts are able to do so. As a consequence the typical book about Linux should assume that the user is familiar with the Python language.
The positive effect is, that the explanation what Linux is about can be shorten drastically. Linux allows to execute self written python programs, consists of a powerful package manager and is distributed for free. If the user have no need for such functionality he probably doesn't need open source software and is recommended to use existing Windows software.
The reason why the market share of Linux is much smaller is because the amount of programmers is small. What we can say for sure is that non programmers won't feel comfortable with Linux. Its not about a certain windows manager like gnome vs xfce and it is not about the position of the start menu, but without programming skills in at least one language the Linux OS doesn't make sense for the user.
From a programmers perspective it is pretty easy to understand the Linux operating system. In comparison to write a medium size software project in Python, the interaction with Linux is much easier. There is no need to call a method in a python program, nor implement a recursive function, but the installation of linux is gui driven and apart from clicking on some buttons no further skills are needed. 99% of existing software engineers are able to install and use Linux with ease.
Let us take a closer look into the numbers. There are 1000 million PC worldwide available and around 27 million programmers. This ratio of 2.7% is the maximum market share of Linux on the desktop. It is not possible to growth the market share of Linux above this level because this would imply that non programmers have installed Linux on the desktop PC in favor of Windows.