Do you have a specific interest in any particular facets of the Pacific Theatre? If so I would start by exploring that interest in detail and in depth. In the process you’ll find yourself asking questions about things you didn’t know you wanted to know. For example, if your interest is in assault landings and you start by reading about the battle for Tarawa, as you learn about why the Gilberts were invaded in the first place you might be intrigued by one of the greater objectives of Operation GALVANIC: to “support the operations in the South-Southwest Pacific and Burma areas by extending pressure on the Japanese.” Now, you may ask yourself, what might those operations be? In following this thread you’ll be led to the campaigns in Burma, New Guinea, and the Solomon Islands, each of which are characterized by their own unique characteristics and fought by troops from several nations, with Indian, British, and Chinese troops constituting the backbone of forces in Burma, Australian and American forces working together in New Guinea, and American forces doing much of the heavy lifting in the Solomons. Depending on how much these interest you you might indulge in your curiosity and explore one or all of them in more detail, which will inevitably lead to the realization of another question that you didn’t you wanted to ask, and the process will repeat itself.

Edited to include: As far as the Ballantine books go I can’t necessarily speak for their veracity because I haven’t read them, but for US Army and US Marine Corps involvement in the war both branch histories are available for free online at https://history.army.mil/html/bookshelves/collect/usaww2.html and https://www.ibiblio.org/hyperwar/USMC/index.html respectively. Both of these series are very reliable, and are very detailed, very in depth works that are meant to trace the events of the war as they occurred from the battalion level up to the Combined Chiefs of Staff. Samuel Eliot Morison’s 14 volume History of US Naval Operations in World War II is not available online and is dated (as well as biased in some areas, notably his treatment of Fletcher) but remains a good starting point to dive into US naval operations and find those questions you didn’t know you had. The Air Force does have their history available online for free, located here https://www.afhistory.af.mil/FAQs/Fact-Sheets/Article/458967/the-u-s-army-air-forces-in-world-war-ii/ - I’ve never really delved into it much so I can’t necessarily say how well it’s stood the test of time, but it is available. Perhaps someone with more exposure to it can speak to its usefulness.

I link you to the branch histories because they’re available and because you can more or less pick a topic and immediately dive into it, at least as it relates to American operations within the Pacific. The China Burma India subset within the Army’s series delves heavily into multinational perspectives as well.

If I may ask do you have any specific interests?