"The Interior Design Handbook" by Frida Ramstedt: This book is a classic for a reason. It covers everything from the basics of space planning and color theory to more advanced topics like lighting and furniture selection. It's a great resource for beginners and experienced designers alike.
"The New Design Rules" by Emily Henderson: This book is a more modern take on interior design, with a focus on creating personal and livable spaces. Henderson's tips are practical and easy to follow, and she has a great eye for style.
Principal
3moLSM just continues, as they have for at least 30 years, raising the bar for design excellence in the interiors space. I've worked, in one capacity or another, with the following 4 interiors firms that I consider to be in a league all their own: LSM in DC; Gary Lee in Chicago; Lauren Rottet in Houston; and Henry Goldston (AREA) in LA.