Assessing the quality of Solomon's reign is a difficult one indeed as we cannot be absolutely sure how accurate the biblical account of his life is. The writer of 1 Kings presents two sides of this king: that of the wise man who "loved Yahweh" (1 Ki.3:3) and who "pleased Yahweh" (v.10), and of the man who lived in decadent luxury, eventually prostituting himself to the religions of his foreign wives.
Solomon inherited from his father David a kingdom united politically, economically and militarily. Indeed it could be said that Solomon was born with the proverbial 'silver spoon in his mouth'. His father had established a powerful middle wastern nation and has earned the respect of his neighbours. Israel was on the map and it remained for Solomon to build on David's secure foundation. He was Israel's first hereditary monarch and in principle had absolute power, since the monarchy possessed a sacral character. To begin with Solomon remained in favour with Yahweh though for how long we do not know. The writer of 1 Kings tells us he permitted to sacrifice "at the high places" (v.2), old Canaanite altares, even though this was forbidden in the Mosaic Law. he entered political marriages to ensure politicallt stable frontiers with his neighbours and to keep Israel's subject peoples happy. The marrying of foreign wives was, of course, forbidden, but what was worse still, they did not abandon their pagan religions. In his old age Solomon began worshipping these pagan deities too in order to please his wives. We can only speculate what might have happened to Israel had Solomon lived a totally righteous life, marrying only covenant women of Israel and strictly enforcing Israel's monotheism.
That Solomon was corrupted by money seems likely; his extravent building projects got him into debt with his main contractor, Hiram of Tyre, forcing him in the end to give the Cabul territory in the north of his country to Phoenicia. His father was faced with troubles when he committed murder and adultery; Solomon faced insurrection from his subject nations like Edom and Aram (Syria) when he turned to pagan gods. His love of opulence made him into a despised dictator, forcing Israelites and Canaanites into forced labour in order to pay for his huge bills. His shabby treatment of the tribes and their traditions, the massive taxation, and the increasingly wide gap between rich and poor, created deep resentments among the people. When he died these resentments exploded, causing the permanent division between Israel in the North and Judah in the South, with the loss of much imperial territory too.
Would Israel have been better off without the kingship of Solomon? I think so. Though Israel became rich and famous, neither of these had much meaning except for the powerful few. Yahweh had never intended Israel to become a monarchy in the first place; the old Tribal Confederacy had been Israel's ideal, a perfect theocracy. Only rebellion by the people caused the theocracy to crumble, leading ultimately to a kingdhip. David could have been the perfect king, notwithstanding the the Confederate ideal, but he lost his soul because of his action against Uriah. Politically the kingdom of David was a necessity, but it was only a necessity because of rebellion! Even the kingdom could have been a success had righteousness prevailed, but with so much centralised power, temptation was strong, and even the legendary wise Solomon succumbed.
In conclusion, politically speaking Solomon's kingship was necessary for Israel's survival, but religiously it was a disaster. It provided no safeguards against corruption and led ultimately, many generations later, to the total destruction of the Northern Kingdom and to the enslavement of the Southern. Had Israel remained true to her faith in the beginning there never would have been a kingdom nor a Solomon. Theocracy would have prevailed and Yahweh would have been Israel's only King. But even if we accept that the kingdom was there to stay Solomon nevertheless betrayed his responsibilities. In many ways he was like King Saul; Saul was torn between the Confederacy and the Kingdom - Solomon was torn between the Theocratic Kingdom and the Worldly Kingdom of Pleasure and Power. Both rebelled against Yahweh, and both reaped the whirlwind for their successors.