The following mistakes have made their way into the final print edition. Some of these were spotted by readers, my sincerest thanks to them.

Chapter 3: Checking Out The Power Of Xcode

p72: At the end of the page, after the numbered list, the following paragraph and code snippet are missing:
We can now check for the presence of the environment variable in our code.
Update the calculateFullPrice method as follows:
func calculateFullPrice()
    var currencyString = "$"

    let envVars = ProcessInfo.processInfo.environment
    if let envVar = envVars["Currency Symbol"]
        currencyString = envVar
        print("Currency Symbol = \(envVar)")

    let rate = rateTextField.doubleValue / 100.0 + 1.0
    let fullPrice = preTaxTextField.doubleValue * rate
    resultLabel.stringValue = currencyString
        + String(format: "%.2f", fullPrice)

Chapter 5: Advanced Swift

p132: The code snippet is incorrect and should read as follows:
extension GridMovement
   static func == (lhs: GridMovement, rhs: GridMovement) -> Bool
     return lhs.rows == rhs.rows && lhs.cols == rhs.cols