The Talbot boy, if really their's, would have had blue eyes, Both Talbots had blue eyes, so genetically they could not have produced a child with brown eyes. That would have been a give-away that he was not their blood son.
Heat Wave is less than a week away from being released, yet Beckett is surprised that Castle might write another Nikki Heat novel. If she thought the agreement for Castle shadowing her was for one book, she would have no reason to be calling him when they catch a case as the book is obviously finished.
Niemann-Pick is a genetic inherited disease. A parent would need to be a carrier. After diagnosis, both parents would have been tested and the genetic results would show that neither parent was a biological parent of the child.
When Beckett arrives at the book party one of the photographers yells, "it's Nikki Heat" and all the photographers start taking her picture even though no one knows that Nikki Heat is based on Beckett, or what Beckett even looks like for that matter. There is no hint in his book either because the dedication only refers to her as KB, and the book has just been published so there would be no time to investigate and discover it is Beckett.
Perlmutter states that stainless steel crowns are no longer used in the USA so she must have been from an Eastern Europe. This is simply not true. While adults do usually opt for tooth coloured crowns for cosmetic reasons, stainless steel crowns are still used across the world. Particularly when cost, complexity, patient age and patient co-operation for the work are factors.