The question number 1 is "what book can I get?"
Even though I have thought for very long about which one would be "the one", I cannot decide. I am linking my LibraryThing page here and you can see for yourself what books I own or want to own, and recommend.
Some of these are not specific to autism intervention, but they have everything to do with it. From Skinner's Science and Human Behavior (also em Português) to Murray Sidman's Coercion and Its Fallout, to any research methodology books you might see there, these have been the foundation of my education as a behavior analyst. I believe that they were major contributors to how I work today, to how much I know, and to how much I know what I still don't know. The discussion around graduate applied behavior analysis training with emphasis on research versus practice is still a current one, and my 2 cents go to emphasis on behavior analytical training before practice training; theory and methodology, then practice. And I am still collecting arguments on both views to complete my own, and especially to define the scope of the practitioner's work.
For parents new to the field, who are considering or starting early intervention with their child, I usually suggest the introduction by Buchanan and Weiss (2006), or Sandra Harris' s Right From the Start. The Me-Book, Work in Progress, I recommend later, when ABA is "a go". And for those who have been through these and similar books, and are looking for more substantial knowledge on Applied Behavior Analysis, Martin and Pear's Behavior Modification: What It Is and How to Do It is sure to provide friendly writing style.
Several of the books are the more "how to do" and specific to a strategy or target behavior, like social skills, activity schedules, discrete-trials teaching.
And, of course, Ethics for Behavior Analysts is a must.
Have a great week!