What to read after Objective-C Programming Nuts and bolts?

Objective-C Programming Nuts and bolts provides a clear and concise overview of the programming language, describes its key features and APIs, and presents recommendations for developing iOS and OS X apps using Objective-C. It is written for readers who want a general understanding of Apple Objective-C technology on the Mac along with developers who want to quickly get started with the language. Very quickly, you will have a solid understanding of Objective-C and be ready to begin using it on your projects!
The book includes a complete overview of the latest enhancements to the Objective-C language, including generics, nullability annotations, and other features. The book is divided into two parts; Part One provides an introduction to object-oriented programming with Objective-C, describes the software development environment for the iOS and OS X platforms, and summarizes key features of the language. Part Two is more focused on application development - it features an in-depth look at the principal components of Objective-C programs, along with a detailed review of the key frameworks and services used for Objective-C application development. The book concludes with a summary and a list of useful references for programming with Objective-C.