A few days ago the subject of Col Vachee's book was brought up. In a follow-up to that subject, I have found Vachee to be basic hero-worship of Napoleon and that it demonstrates an incredible level of non-understanding on how the staff system of the Grande Armee actually functioned. Berthier, as usual, is underestimated and that is not surprising in Vachee since Jomini is one of the references used by Vachee.
Jomini hated Berthier because of various imagined 'slights' by Berthier to Jomini, beginning when Jomini was a civilian ADC to Ney in 1805. Jomini had a problem with authority, especially with those who were his seniors. He was rightfully and justly upbraided by Berthier and given the quick-course on French staff procedures. Jomini also clashed with his superior, Hogendorp, during the Russian campaign as well as Ney's chief of staff, Dutaillis.
Anyways, Martin van Creveld also mentioned that Vachee's book was blatant 'hero worship' of Napoleon. I don't believe Vachee to be a reliable work for use as a reference, but it is an interesting read.