Reddit reviews Building Embedded Systems: Programmable Hardware

Not sure what your budget is (buy used books or South Asia editions), but you may find the following useful :-)

Also, unless required, avoid programming in assembly but use C/C++ exclusively. This allows you to carry over much of your acquired knowledge across various MCU families.

• Make: AVR Programming This will teach you programming directly-to-the-metal on AVR using C. If you have the Arduino IDE installed, you already have the "avr-gcc" compiler toolchain as part of the package and hence you just need to setup your path and use the the toolchain in your Makefile. The book takes you by hand and shows you everything. Note that you can use the same Arduino board to do both "Arduino language" programming and "AVR C" programming.
  
  
• Designing Embedded Hardware Excellent overview of the hardware aspects of Embedded Systems. As a Software guy, this book is the one which clarified hardware for me.
  
  
• Building Embedded Systems: Programmable Hardware A very good book on all practical aspects of embedded programming. Hard-won knowledge which will make you a "professional" embedded engineer.
  
  
• Introduction to Embedded Systems: Using Microcontrollers and the MSP430 Excellent and comprehensive textbook detailing the hardware and software aspects of embedded systems. Every topic starts with an illustrated overview of the hardware and then shows you how to program for it.
  
  
• Embedded C Introductory book on C programming for 8051. The example code is simple and direct thus enabling you to grasp the concepts clearly.
  
  
• Patterns for Time-Triggered Embedded Systems Comprehensive and full of C code showing how to program all standard peripherals for an 8051. You can translate the code to your favourite MCU family. The book is available for free from the author's company website.
  
  
• ARM System Developer's Guide An oldie but still the best for firmware programming on the ARM microprocessor.
  
  
• Practical Microcontroller Engineering with ARM technology An exhaustive book on programming the Tiva version of the ARM Cortex-M4 MCU. The book reads like a manual but the ARM Cortex is complex enough that there is no easy way to learn it.
  
  
• The Engineering of Reliable Embedded Systems Advanced book showing how to implement industrial quality embedded software on various ARM platforms. The 1st edition of the book was available for free on the web.
  
  and finally;
  
  
• Computer Systems: A Programmer's Perspective A must-read textbook to understand the low-level details for a x86/x86-64 system. Many of these details are similar for MCUs and hence you will understand them better.